Update README.md

.github/workflows/build-test.sh

@@ -6,6 +6,6 @@ echo 'set -eu' > test.sh
 for p in $(go list ./...); do
   dir=".${p#github.com/ncruces/go-sqlite3}"
   name="$(basename "$p").test"
-  (cd ${dir}; go test -c)
-  [ -f "${dir}/${name}" ] && echo "(cd ${dir}; ./${name} ${TESTFLAGS})" >> test.sh
+  (cd ${dir}; go test -c ${BUILDFLAGS:-})
+  [ -f "${dir}/${name}" ] && echo "(cd ${dir}; ./${name} ${TESTFLAGS:-})" >> test.sh
 done

.github/workflows/cross.sh

@@ -17,11 +17,13 @@ echo aix           ; GOOS=aix       GOARCH=ppc64 go build .
 echo js            ; GOOS=js        GOARCH=wasm  go build .
 echo wasip1        ; GOOS=wasip1    GOARCH=wasm  go build .
 echo linux-flock   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_flock .
-echo linux-noshm   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_noshm .
+echo linux-dotlk   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_dotlk .
 echo linux-nosys   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_nosys .
 echo darwin-flock  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_flock .
-echo darwin-noshm  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_noshm .
+echo darwin-dotlk  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_dotlk .
 echo darwin-nosys  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_nosys .
+echo windows-dotlk ; GOOS=windows   GOARCH=amd64 go build -tags sqlite3_dotlk .
 echo windows-nosys ; GOOS=windows   GOARCH=amd64 go build -tags sqlite3_nosys .
+echo freebsd-dotlk ; GOOS=freebsd   GOARCH=amd64 go build -tags sqlite3_dotlk .
 echo freebsd-nosys ; GOOS=freebsd   GOARCH=amd64 go build -tags sqlite3_nosys .
-echo solaris-flock ; GOOS=solaris   GOARCH=amd64 go build -tags sqlite3_flock .
+echo solaris-dotlk ; GOOS=solaris   GOARCH=amd64 go build -tags sqlite3_dotlk .

.github/workflows/repro.sh

@@ -3,13 +3,13 @@ set -euo pipefail
 
 if [[ "$OSTYPE" == "linux"* ]]; then
   WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-linux.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_119/binaryen-version_119-x86_64-linux.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-x86_64-linux.tar.gz"
 elif [[ "$OSTYPE" == "darwin"* ]]; then
   WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-macos.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_119/binaryen-version_119-x86_64-macos.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-arm64-macos.tar.gz"
 elif [[ "$OSTYPE" == "msys" || "$OSTYPE" == "cygwin" ]]; then
   WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-windows.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_119/binaryen-version_119-x86_64-windows.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-x86_64-windows.tar.gz"
 fi
 
 # Download tools

.github/workflows/test.yml

@@ -9,6 +9,10 @@ on:
       - '**.wasm.bz2'
   pull_request:
     branches: [ "main" ]
+    paths:
+      - '**.go'
+      - '**.wasm'
+      - '**.wasm.bz2'
   workflow_dispatch:
 
 jobs:
@@ -48,17 +52,17 @@ jobs:
     - name: Test
       run: go test -v ./... -bench . -benchtime=1x
 
+    - name: Test no locks
+      run: go test -v -tags sqlite3_nosys ./...
+      if: matrix.os == 'ubuntu-latest'
+
     - name: Test BSD locks
       run: go test -v -tags sqlite3_flock ./...
       if: matrix.os == 'macos-latest'
 
-    - name: Test no shared memory
-      run: go test -v -tags sqlite3_noshm ./...
-      if: matrix.os == 'ubuntu-latest'
-
-    - name: Test no locks
-      run: go test -v -tags sqlite3_nosys ./...
-      if: matrix.os == 'ubuntu-latest'
+    - name: Test dot locks
+      run: go test -v -tags sqlite3_dotlk ./...
+      if: matrix.os != 'windows-latest'
 
     - name: Test GORM
       shell: bash
@@ -190,6 +194,7 @@ jobs:
       env:
         GOOS: solaris
         TESTFLAGS: '-test.v -test.short'
+        BUILDFLAGS: '-tags sqlite3_dotlk'
       run: .github/workflows/build-test.sh
 
     - name: Test Solaris

context.go

@@ -89,6 +89,7 @@ func (ctx Context) ResultText(value string) {
 }
 
 // ResultRawText sets the text result of the function to a []byte.
+// Returning a nil slice is the same as calling [Context.ResultNull].
 //
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultRawText(value []byte) {

driver/example_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package driver_test
 

ext/regexp/regexp.go

@@ -1,9 +1,11 @@
 // Package regexp provides additional regular expression functions.
 //
 // It provides the following Unicode aware functions:
-//   - regexp_like(),
-//   - regexp_substr(),
-//   - regexp_replace(),
+//   - regexp_like(text, pattern),
+//   - regexp_count(text, pattern [, start]),
+//   - regexp_instr(text, pattern [, start [, N [, endoption [, subexpr ]]]]),
+//   - regexp_substr(text, pattern [, start [, N [, subexpr ]]]),
+//   - regexp_replace(text, pattern, replacement [, start [, N ]]),
 //   - and a REGEXP operator.
 //
 // The implementation uses Go [regexp/syntax] for regular expressions.
@@ -14,6 +16,7 @@ package regexp
 import (
 	"errors"
 	"regexp"
+	"strings"
 
 	"github.com/ncruces/go-sqlite3"
 )
@@ -24,8 +27,39 @@ func Register(db *sqlite3.Conn) error {
 	return errors.Join(
 		db.CreateFunction("regexp", 2, flags, regex),
 		db.CreateFunction("regexp_like", 2, flags, regexLike),
+		db.CreateFunction("regexp_count", 2, flags, regexCount),
+		db.CreateFunction("regexp_count", 3, flags, regexCount),
+		db.CreateFunction("regexp_instr", 2, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 3, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 4, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 5, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 6, flags, regexInstr),
 		db.CreateFunction("regexp_substr", 2, flags, regexSubstr),
-		db.CreateFunction("regexp_replace", 3, flags, regexReplace))
+		db.CreateFunction("regexp_substr", 3, flags, regexSubstr),
+		db.CreateFunction("regexp_substr", 4, flags, regexSubstr),
+		db.CreateFunction("regexp_substr", 5, flags, regexSubstr),
+		db.CreateFunction("regexp_replace", 3, flags, regexReplace),
+		db.CreateFunction("regexp_replace", 4, flags, regexReplace),
+		db.CreateFunction("regexp_replace", 5, flags, regexReplace))
+}
+
+// GlobPrefix returns a GLOB for a regular expression
+// appropriate to take advantage of the [LIKE optimization]
+// in a query such as:
+//
+//	SELECT column WHERE column GLOB :glob_prefix AND column REGEXP :regexp
+//
+// [LIKE optimization]: https://sqlite.org/optoverview.html#the_like_optimization
+func GlobPrefix(re *regexp.Regexp) string {
+	prefix, complete := re.LiteralPrefix()
+	i := strings.IndexAny(prefix, "*?[")
+	if i < 0 {
+		if complete {
+			return prefix
+		}
+		i = len(prefix)
+	}
+	return prefix[:i] + "*"
 }
 
 func load(ctx sqlite3.Context, i int, expr string) (*regexp.Regexp, error) {
@@ -44,35 +78,163 @@ func load(ctx sqlite3.Context, i int, expr string) (*regexp.Regexp, error) {
 func regex(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	re, err := load(ctx, 0, arg[0].Text())
 	if err != nil {
-		ctx.ResultError(err) // notest
-	} else {
-		ctx.ResultBool(re.Match(arg[1].RawText()))
+		ctx.ResultError(err)
+		return // notest
 	}
+	text := arg[1].RawText()
+	ctx.ResultBool(re.Match(text))
 }
 
 func regexLike(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	re, err := load(ctx, 1, arg[1].Text())
 	if err != nil {
-		ctx.ResultError(err) // notest
-	} else {
-		ctx.ResultBool(re.Match(arg[0].RawText()))
+		ctx.ResultError(err)
+		return // notest
 	}
+
+	text := arg[0].RawText()
+	ctx.ResultBool(re.Match(text))
+}
+
+func regexCount(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	if len(arg) > 2 {
+		pos := arg[2].Int()
+		text = text[skip(text, pos):]
+	}
+	ctx.ResultInt(len(re.FindAll(text, -1)))
 }
 
 func regexSubstr(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	re, err := load(ctx, 1, arg[1].Text())
 	if err != nil {
-		ctx.ResultError(err) // notest
-	} else {
-		ctx.ResultRawText(re.Find(arg[0].RawText()))
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	var pos, n, subexpr int
+	if len(arg) > 2 {
+		pos = arg[2].Int()
+	}
+	if len(arg) > 3 {
+		n = arg[3].Int()
+	}
+	if len(arg) > 4 {
+		subexpr = arg[4].Int()
+	}
+
+	loc := regexFind(re, text, pos, n, subexpr)
+	if loc != nil {
+		ctx.ResultRawText(text[loc[0]:loc[1]])
+	}
+}
+
+func regexInstr(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	var pos, n, end, subexpr int
+	if len(arg) > 2 {
+		pos = arg[2].Int()
+	}
+	if len(arg) > 3 {
+		n = arg[3].Int()
+	}
+	if len(arg) > 4 && arg[4].Bool() {
+		end = 1
+	}
+	if len(arg) > 5 {
+		subexpr = arg[5].Int()
+	}
+
+	loc := regexFind(re, text, pos, n, subexpr)
+	if loc != nil {
+		ctx.ResultInt(loc[end] + 1)
 	}
 }
 
 func regexReplace(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	re, err := load(ctx, 1, arg[1].Text())
 	if err != nil {
-		ctx.ResultError(err) // notest
-	} else {
-		ctx.ResultRawText(re.ReplaceAll(arg[0].RawText(), arg[2].RawText()))
+		ctx.ResultError(err)
+		return // notest
 	}
+
+	text := arg[0].RawText()
+	repl := arg[2].RawText()
+	var pos, n int
+	if len(arg) > 3 {
+		pos = arg[3].Int()
+	}
+	if len(arg) > 4 {
+		n = arg[4].Int()
+	}
+
+	res := text
+	pos = skip(text, pos)
+	if n > 0 {
+		all := re.FindAllSubmatchIndex(text[pos:], n)
+		if n <= len(all) {
+			loc := all[n-1]
+			res = text[:pos+loc[0]]
+			res = re.Expand(res, repl, text[pos:], loc)
+			res = append(res, text[pos+loc[1]:]...)
+		}
+	} else {
+		res = append(text[:pos], re.ReplaceAll(text[pos:], repl)...)
+	}
+	ctx.ResultRawText(res)
+}
+
+func regexFind(re *regexp.Regexp, text []byte, pos, n, subexpr int) (loc []int) {
+	pos = skip(text, pos)
+	text = text[pos:]
+
+	if n <= 1 {
+		if subexpr == 0 {
+			loc = re.FindIndex(text)
+		} else {
+			loc = re.FindSubmatchIndex(text)
+		}
+	} else {
+		if subexpr == 0 {
+			all := re.FindAllIndex(text, n)
+			if n <= len(all) {
+				loc = all[n-1]
+			}
+		} else {
+			all := re.FindAllSubmatchIndex(text, n)
+			if n <= len(all) {
+				loc = all[n-1]
+			}
+		}
+	}
+
+	if 2+2*subexpr <= len(loc) {
+		loc = loc[2*subexpr : 2+2*subexpr]
+		loc[0] += pos
+		loc[1] += pos
+		return loc
+	}
+	return nil
+}
+
+func skip(text []byte, start int) int {
+	for pos := range string(text) {
+		if start--; start <= 0 {
+			return pos
+		}
+	}
+	return len(text)
 }

ext/regexp/regexp_test.go

@@ -1,6 +1,8 @@
 package regexp
 
 import (
+	"database/sql"
+	"regexp"
 	"testing"
 
 	"github.com/ncruces/go-sqlite3/driver"
@@ -29,18 +31,47 @@ func TestRegister(t *testing.T) {
 		{`regexp_like('Hello', 'elo')`, "0"},
 		{`regexp_like('Hello', 'ell')`, "1"},
 		{`regexp_like('Hello', 'el.')`, "1"},
+		{`regexp_count('Hello', 'l')`, "2"},
+		{`regexp_instr('Hello', 'el.')`, "2"},
+		{`regexp_instr('Hello', '.', 6)`, ""},
 		{`regexp_substr('Hello', 'el.')`, "ell"},
 		{`regexp_replace('Hello', 'llo', 'll')`, "Hell"},
+		// https://www.postgresql.org/docs/current/functions-matching.html
+		{`regexp_count('ABCABCAXYaxy', 'A.')`, "3"},
+		{`regexp_count('ABCABCAXYaxy', '(?i)A.', 1)`, "4"},
+		{`regexp_instr('number of your street, town zip, FR', '[^,]+', 1, 2)`, "23"},
+		{`regexp_instr('ABCDEFGHI', '(?i)(c..)(...)', 1, 1, 0, 2)`, "6"},
+		{`regexp_substr('number of your street, town zip, FR', '[^,]+', 1, 2)`, " town zip"},
+		{`regexp_substr('ABCDEFGHI', '(?i)(c..)(...)', 1, 1, 2)`, "FGH"},
+		{`regexp_replace('foobarbaz', 'b..', 'X', 1, 1)`, "fooXbaz"},
+		{`regexp_replace('foobarbaz', 'b..', 'X')`, "fooXX"},
+		{`regexp_replace('foobarbaz', 'b(..)', 'X${1}Y')`, "fooXarYXazY"},
+		{`regexp_replace('A PostgreSQL function', '(?i)a|e|i|o|u', 'X', 1, 0)`, "X PXstgrXSQL fXnctXXn"},
+		{`regexp_replace('A PostgreSQL function', '(?i)a|e|i|o|u', 'X', 1, 3)`, "A PostgrXSQL function"},
+		// https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/REGEXP_COUNT.html
+		{`regexp_count('123123123123123', '(12)3', 1)`, "5"},
+		{`regexp_count('123123123123', '123', 3)`, "3"},
+		{`regexp_instr('500 Oracle Parkway, Redwood Shores, CA', '[^ ]+', 1, 6)`, "37"},
+		{`regexp_instr('500 Oracle Parkway, Redwood Shores, CA', '(?i)[s|r|p][[:alpha:]]{6}', 3, 2, 1)`, "28"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 1)`, "1"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 2)`, "4"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 4)`, "7"},
+		{`regexp_substr('500 Oracle Parkway, Redwood Shores, CA', ',[^,]+,')`, ", Redwood Shores,"},
+		{`regexp_substr('http://www.example.com/products', 'http://([[:alnum:]]+\.?){3,4}/?')`, "http://www.example.com/"},
+		{`regexp_substr('1234567890', '(123)(4(56)(78))', 1, 1, 1)`, "123"},
+		{`regexp_substr('1234567890', '(123)(4(56)(78))', 1, 1, 4)`, "78"},
+		{`regexp_substr('123123123123', '1(.)3', 3, 2, 1)`, "2"},
+		{`regexp_replace('500   Oracle     Parkway,    Redwood  Shores, CA', '( ){2,}', ' ')`, "500 Oracle Parkway, Redwood Shores, CA"},
 	}
 
 	for _, tt := range tests {
-		var got string
+		var got sql.NullString
 		err := db.QueryRow(`SELECT ` + tt.test).Scan(&got)
 		if err != nil {
 			t.Fatal(err)
 		}
-		if got != tt.want {
-			t.Errorf("got %q, want %q", got, tt.want)
+		if got.String != tt.want {
+			t.Errorf("got %q, want %q", got.String, tt.want)
 		}
 	}
 }
@@ -58,6 +89,8 @@ func TestRegister_errors(t *testing.T) {
 	tests := []string{
 		`'' REGEXP ?`,
 		`regexp_like('', ?)`,
+		`regexp_count('', ?)`,
+		`regexp_instr('', ?)`,
 		`regexp_substr('', ?)`,
 		`regexp_replace('', ?, '')`,
 	}
@@ -69,3 +102,25 @@ func TestRegister_errors(t *testing.T) {
 		}
 	}
 }
+
+func TestGlobPrefix(t *testing.T) {
+	tests := []struct {
+		re   string
+		want string
+	}{
+		{``, ""},
+		{`a`, "a"},
+		{`a*`, "*"},
+		{`a+`, "a*"},
+		{`ab*`, "a*"},
+		{`ab+`, "ab*"},
+		{`a\?b`, "a*"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.re, func(t *testing.T) {
+			if got := GlobPrefix(regexp.MustCompile(tt.re)); got != tt.want {
+				t.Errorf("GlobPrefix() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

gormlite/go.mod

@@ -5,7 +5,7 @@ go 1.21
 toolchain go1.23.0
 
 require (
-	github.com/ncruces/go-sqlite3 v0.18.4
+	github.com/ncruces/go-sqlite3 v0.20.0
 	gorm.io/gorm v1.25.12
 )
 

gormlite/go.sum

@@ -2,8 +2,8 @@ github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD
 github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
 github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
-github.com/ncruces/go-sqlite3 v0.18.4 h1:Je8o3y33MDwPYY/Cacas8yCsuoUzpNY/AgoSlN2ekyE=
-github.com/ncruces/go-sqlite3 v0.18.4/go.mod h1:4HLag13gq1k10s4dfGBhMfRVsssJRT9/5hYqVM9RUYo=
+github.com/ncruces/go-sqlite3 v0.20.0 h1:/nBLvYxj7sk9S6y57nmMFvoQ/KJtGo0pNi8J80s8oJU=
+github.com/ncruces/go-sqlite3 v0.20.0/go.mod h1:yL4ZNWGsr1/8pcLfpPW1RT1WFdvyeHonrgIwwi4rvkg=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
 github.com/tetratelabs/wazero v1.8.1 h1:NrcgVbWfkWvVc4UtT4LRLDf91PsOzDzefMdwhLfA550=

internal/testcfg/testcfg.go

@@ -19,7 +19,8 @@ func init() {
 		path := filepath.Join(os.TempDir(), "wazero")
 		if err := os.MkdirAll(path, 0777); err == nil {
 			if cache, err := wazero.NewCompilationCacheWithDir(path); err == nil {
-				sqlite3.RuntimeConfig.WithCompilationCache(cache)
+				sqlite3.RuntimeConfig = sqlite3.RuntimeConfig.
+					WithCompilationCache(cache)
 			}
 		}
 	}

internal/util/mmap.go

@@ -1,4 +1,4 @@
-//go:build unix && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_noshm || sqlite3_nosys)
+//go:build unix && !sqlite3_nosys
 
 package util
 
@@ -55,10 +55,10 @@ type MappedRegion struct {
 	used bool
 }
 
-func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32, prot int) (*MappedRegion, error) {
+func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32, readOnly bool) (*MappedRegion, error) {
 	s := ctx.Value(moduleKey{}).(*moduleState)
 	r := s.new(ctx, mod, size)
-	err := r.mmap(f, offset, prot)
+	err := r.mmap(f, offset, readOnly)
 	if err != nil {
 		return nil, err
 	}
@@ -75,7 +75,11 @@ func (r *MappedRegion) Unmap() error {
 	return err
 }
 
-func (r *MappedRegion) mmap(f *os.File, offset int64, prot int) error {
+func (r *MappedRegion) mmap(f *os.File, offset int64, readOnly bool) error {
+	prot := unix.PROT_READ
+	if !readOnly {
+		prot |= unix.PROT_WRITE
+	}
 	_, err := unix.MmapPtr(int(f.Fd()), offset, r.addr, uintptr(r.size),
 		prot, unix.MAP_SHARED|unix.MAP_FIXED)
 	r.used = err == nil

internal/util/mmap_other.go

@@ -1,4 +1,4 @@
-//go:build !unix || !(386 || arm || amd64 || arm64 || riscv64 || ppc64le) || sqlite3_noshm || sqlite3_nosys
+//go:build !unix || sqlite3_nosys
 
 package util
 

internal/util/mmap_windows.go

@@ -0,0 +1,53 @@
+//go:build !sqlite3_nosys
+
+package util
+
+import (
+	"context"
+	"os"
+	"reflect"
+	"unsafe"
+
+	"github.com/tetratelabs/wazero/api"
+	"golang.org/x/sys/windows"
+)
+
+type MappedRegion struct {
+	windows.Handle
+	Data []byte
+	addr uintptr
+}
+
+func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32) (*MappedRegion, error) {
+	h, err := windows.CreateFileMapping(windows.Handle(f.Fd()), nil, windows.PAGE_READWRITE, 0, 0, nil)
+	if h == 0 {
+		return nil, err
+	}
+
+	a, err := windows.MapViewOfFile(h, windows.FILE_MAP_WRITE,
+		uint32(offset>>32), uint32(offset), uintptr(size))
+	if a == 0 {
+		windows.CloseHandle(h)
+		return nil, err
+	}
+
+	res := &MappedRegion{Handle: h, addr: a}
+	// SliceHeader, although deprecated, avoids a go vet warning.
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&res.Data))
+	sh.Len = int(size)
+	sh.Cap = int(size)
+	sh.Data = a
+	return res, nil
+}
+
+func (r *MappedRegion) Unmap() error {
+	if r.Data == nil {
+		return nil
+	}
+	err := windows.UnmapViewOfFile(r.addr)
+	if err != nil {
+		return err
+	}
+	r.Data = nil
+	return windows.CloseHandle(r.Handle)
+}

stmt.go

@@ -255,6 +255,7 @@ func (s *Stmt) BindText(param int, value string) error {
 
 // BindRawText binds a []byte to the prepared statement as text.
 // The leftmost SQL parameter has an index of 1.
+// Binding a nil slice is the same as calling [Stmt.BindNull].
 //
 // https://sqlite.org/c3ref/bind_blob.html
 func (s *Stmt) BindRawText(param int, value []byte) error {

tests/bradfitz/sql_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package bradfitz
 

vfs/README.md

@@ -15,24 +15,23 @@ The main differences are [file locking](#file-locking) and [WAL mode](#write-ahe
 
 POSIX advisory locks, which SQLite uses on Unix, are
 [broken by design](https://github.com/sqlite/sqlite/blob/b74eb0/src/os_unix.c#L1073-L1161).
-
-On Linux and macOS, this package uses
+Instead, on Linux and macOS, this package uses
 [OFD locks](https://www.gnu.org/software/libc/manual/html_node/Open-File-Description-Locks.html)
 to synchronize access to database files.
-OFD locks are fully compatible with POSIX advisory locks.
 
 This package can also use
 [BSD locks](https://man.freebsd.org/cgi/man.cgi?query=flock&sektion=2),
 albeit with reduced concurrency (`BEGIN IMMEDIATE` behaves like `BEGIN EXCLUSIVE`).
-On BSD, macOS, and illumos, BSD locks are fully compatible with POSIX advisory locks;
-on Linux and z/OS, they are fully functional, but incompatible;
-elsewhere, they are very likely broken.
 BSD locks are the default on BSD and illumos,
 but you can opt into them with the `sqlite3_flock` build tag.
 
 On Windows, this package uses `LockFileEx` and `UnlockFileEx`,
 like SQLite.
 
+You can also opt into a cross-platform locking implementation
+with the `sqlite3_dotlk` build tag.
+The only requirement is an atomic `os.Mkdir`.
+
 Otherwise, file locking is not supported, and you must use
 [`nolock=1`](https://sqlite.org/uri.html#urinolock)
 (or [`immutable=1`](https://sqlite.org/uri.html#uriimmutable))
@@ -46,7 +45,7 @@ to check if your build supports file locking.
 
 ### Write-Ahead Logging
 
-On little-endian Unix, this package uses `mmap` to implement
+On Unix, this package may use `mmap` to implement
 [shared-memory for the WAL-index](https://sqlite.org/wal.html#implementation_of_shared_memory_for_the_wal_index),
 like SQLite.
 
@@ -55,6 +54,11 @@ a WAL database can only be accessed by a single proccess.
 Other processes that attempt to access a database locked with BSD locks,
 will fail with the [`SQLITE_PROTOCOL`](https://sqlite.org/rescode.html#protocol) error code.
 
+On Windows, this package may use `MapViewOfFile`, like SQLite.
+
+You can also opt into a cross-platform, in-process, memory sharing implementation
+with the `sqlite3_dotlk` build tag.
+
 Otherwise, [WAL support is limited](https://sqlite.org/wal.html#noshm),
 and `EXCLUSIVE` locking mode must be set to create, read, and write WAL databases.
 To use `EXCLUSIVE` locking mode with the
@@ -67,7 +71,7 @@ to check if your build supports shared memory.
 
 ### Batch-Atomic Write
 
-On 64-bit Linux, this package supports
+On Linux, this package may support
 [batch-atomic writes](https://sqlite.org/cgi/src/technote/714)
 on the F2FS filesystem.
 
@@ -86,27 +90,27 @@ The implementation is compatible with SQLite's
 ### Build Tags
 
 The VFS can be customized with a few build tags:
-- `sqlite3_flock` forces the use of BSD locks; it can be used on z/OS to enable locking,
-  and elsewhere to test BSD locks.
-- `sqlite3_nosys` prevents importing [`x/sys`](https://pkg.go.dev/golang.org/x/sys);
-  disables locking _and_ shared memory on all platforms.
-- `sqlite3_noshm` disables shared memory on all platforms.
+- `sqlite3_flock` forces the use of BSD locks.
+- `sqlite3_dotlk` forces the use of dot-file locks.
+- `sqlite3_nosys` prevents importing [`x/sys`](https://pkg.go.dev/golang.org/x/sys).
 
 > [!IMPORTANT]
 > The default configuration of this package is compatible with the standard
 > [Unix and Windows SQLite VFSes](https://sqlite.org/vfs.html#multiple_vfses);
 > `sqlite3_flock` builds are compatible with the
-> [`unix-flock` VFS](https://sqlite.org/compile.html#enable_locking_style).
+> [`unix-flock` VFS](https://sqlite.org/compile.html#enable_locking_style);
+> `sqlite3_dotlk` builds are compatible with the
+> [`unix-dotfile` VFS](https://sqlite.org/compile.html#enable_locking_style).
 > If incompatible file locking is used, accessing databases concurrently with
 > _other_ SQLite libraries will eventually corrupt data.
 
 ### Custom VFSes
 
-- [`github.com/ncruces/go-sqlite3/vfs/adiantum`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/adiantum)
-  wraps a VFS to offer encryption at rest.
 - [`github.com/ncruces/go-sqlite3/vfs/memdb`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/memdb)
   implements an in-memory VFS.
 - [`github.com/ncruces/go-sqlite3/vfs/readervfs`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/readervfs)
   implements a VFS for immutable databases.
+- [`github.com/ncruces/go-sqlite3/vfs/adiantum`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/adiantum)
+  wraps a VFS to offer encryption at rest.
 - [`github.com/ncruces/go-sqlite3/vfs/xts`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/xts)
-  wraps a VFS to offer encryption at rest.
+  wraps a VFS to offer encryption at rest.

vfs/adiantum/example_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package adiantum_test
 

vfs/const.go

@@ -234,4 +234,8 @@ const (
 	_SHM_LOCK      _ShmFlag = 2
 	_SHM_SHARED    _ShmFlag = 4
 	_SHM_EXCLUSIVE _ShmFlag = 8
+
+	_SHM_NLOCK = 8
+	_SHM_BASE  = 120
+	_SHM_DMS   = _SHM_BASE + _SHM_NLOCK
 )

vfs/file.go

@@ -35,10 +35,10 @@ func testSymlinks(path string) error {
 
 func (vfsOS) Delete(path string, syncDir bool) error {
 	err := os.Remove(path)
+	if errors.Is(err, fs.ErrNotExist) {
+		return _IOERR_DELETE_NOENT
+	}
 	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
-			return _IOERR_DELETE_NOENT
-		}
 		return err
 	}
 	if runtime.GOOS != "windows" && syncDir {
@@ -151,6 +151,7 @@ func (f *vfsFile) Close() error {
 	if f.shm != nil {
 		f.shm.Close()
 	}
+	f.Unlock(LOCK_NONE)
 	return f.File.Close()
 }
 
@@ -206,10 +207,10 @@ func (f *vfsFile) HasMoved() (bool, error) {
 		return false, err
 	}
 	pi, err := os.Stat(f.Name())
+	if errors.Is(err, fs.ErrNotExist) {
+		return true, nil
+	}
 	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
-			return true, nil
-		}
 		return false, err
 	}
 	return !os.SameFile(fi, pi), nil

vfs/lock.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package vfs
 

vfs/lock_other.go

@@ -1,4 +1,4 @@
-//go:build !(linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) || sqlite3_nosys
+//go:build !(((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 

vfs/memdb/memdb.go

@@ -78,19 +78,15 @@ type memDB struct {
 
 	// +checklocks:dataMtx
 	data []*[sectorSize]byte
-
 	// +checklocks:dataMtx
 	size int64
 
-	// +checklocks:lockMtx
-	shared int32
-	// +checklocks:lockMtx
-	reserved bool
-	// +checklocks:lockMtx
-	pending bool
-
 	// +checklocks:memoryMtx
-	refs int
+	refs int32
+
+	shared   int32 // +checklocks:lockMtx
+	pending  bool  // +checklocks:lockMtx
+	reserved bool  // +checklocks:lockMtx
 
 	lockMtx sync.Mutex
 	dataMtx sync.RWMutex
@@ -253,12 +249,12 @@ func (m *memFile) Unlock(lock vfs.LockLevel) error {
 	m.lockMtx.Lock()
 	defer m.lockMtx.Unlock()
 
-	if m.pending && m.lock >= vfs.LOCK_PENDING {
-		m.pending = false
-	}
-	if m.reserved && m.lock >= vfs.LOCK_RESERVED {
+	if m.lock >= vfs.LOCK_RESERVED {
 		m.reserved = false
 	}
+	if m.lock >= vfs.LOCK_PENDING {
+		m.pending = false
+	}
 	if lock < vfs.LOCK_SHARED {
 		m.shared--
 	}

vfs/os_bsd.go

@@ -1,4 +1,4 @@
-//go:build (freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
 
 package vfs
 

vfs/os_dotlk.go

@@ -0,0 +1,143 @@
+//go:build sqlite3_dotlk
+
+package vfs
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"sync"
+)
+
+var (
+	// +checklocks:vfsDotLocksMtx
+	vfsDotLocks    = map[string]*vfsDotLocker{}
+	vfsDotLocksMtx sync.Mutex
+)
+
+type vfsDotLocker struct {
+	shared   int      // +checklocks:vfsDotLocksMtx
+	pending  *os.File // +checklocks:vfsDotLocksMtx
+	reserved *os.File // +checklocks:vfsDotLocksMtx
+}
+
+func osGetSharedLock(file *os.File) _ErrorCode {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		err := os.Mkdir(name+".lock", 0777)
+		if errors.Is(err, fs.ErrExist) {
+			return _BUSY // Another process has the lock.
+		}
+		if err != nil {
+			return _IOERR_LOCK
+		}
+		locker = &vfsDotLocker{}
+		vfsDotLocks[name] = locker
+	}
+
+	if locker.pending != nil {
+		return _BUSY
+	}
+	locker.shared++
+	return _OK
+}
+
+func osGetReservedLock(file *os.File) _ErrorCode {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		return _IOERR_LOCK
+	}
+
+	if locker.reserved != nil && locker.reserved != file {
+		return _BUSY
+	}
+	locker.reserved = file
+	return _OK
+}
+
+func osGetExclusiveLock(file *os.File, _ *LockLevel) _ErrorCode {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		return _IOERR_LOCK
+	}
+
+	if locker.pending != nil && locker.pending != file {
+		return _BUSY
+	}
+	locker.pending = file
+	if locker.shared > 1 {
+		return _BUSY
+	}
+	return _OK
+}
+
+func osDowngradeLock(file *os.File, _ LockLevel) _ErrorCode {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		return _IOERR_UNLOCK
+	}
+
+	if locker.reserved == file {
+		locker.reserved = nil
+	}
+	if locker.pending == file {
+		locker.pending = nil
+	}
+	return _OK
+}
+
+func osReleaseLock(file *os.File, state LockLevel) _ErrorCode {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		return _IOERR_UNLOCK
+	}
+
+	if locker.shared == 1 {
+		err := os.Remove(name + ".lock")
+		if err != nil && !errors.Is(err, fs.ErrNotExist) {
+			return _IOERR_UNLOCK
+		}
+		delete(vfsDotLocks, name)
+	}
+
+	if locker.reserved == file {
+		locker.reserved = nil
+	}
+	if locker.pending == file {
+		locker.pending = nil
+	}
+	locker.shared--
+	return _OK
+}
+
+func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
+	vfsDotLocksMtx.Lock()
+	defer vfsDotLocksMtx.Unlock()
+
+	name := file.Name()
+	locker := vfsDotLocks[name]
+	if locker == nil {
+		return false, _OK
+	}
+	return locker.reserved != nil, _OK
+}

vfs/os_ofd.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin) && !(sqlite3_flock || sqlite3_nosys)
+//go:build (linux || darwin) && !(sqlite3_flock || sqlite3_dotlk || sqlite3_nosys)
 
 package vfs
 

vfs/os_windows.go

@@ -1,4 +1,4 @@
-//go:build !sqlite3_nosys
+//go:build !(sqlite3_dotlk || sqlite3_nosys)
 
 package vfs
 

vfs/shm.go

@@ -1,20 +1,7 @@
-//go:build (darwin || linux) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_flock || sqlite3_noshm || sqlite3_nosys)
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package vfs
 
-import (
-	"context"
-	"io"
-	"os"
-	"sync"
-	"time"
-
-	"github.com/tetratelabs/wazero/api"
-	"golang.org/x/sys/unix"
-
-	"github.com/ncruces/go-sqlite3/internal/util"
-)
-
 // SupportsSharedMemory is false on platforms that do not support shared memory.
 // To use [WAL without shared-memory], you need to set [EXCLUSIVE locking mode].
 //
@@ -22,12 +9,6 @@ import (
 // [EXCLUSIVE locking mode]: https://sqlite.org/pragma.html#pragma_locking_mode
 const SupportsSharedMemory = true
 
-const (
-	_SHM_NLOCK = 8
-	_SHM_BASE  = 120
-	_SHM_DMS   = _SHM_BASE + _SHM_NLOCK
-)
-
 func (f *vfsFile) SharedMemory() SharedMemory { return f.shm }
 
 // NewSharedMemory returns a shared-memory WAL-index
@@ -41,172 +22,5 @@ func NewSharedMemory(path string, flags OpenFlag) SharedMemory {
 	if flags&OPEN_MAIN_DB == 0 || flags&(OPEN_DELETEONCLOSE|OPEN_MEMORY) != 0 {
 		return nil
 	}
-	return &vfsShm{
-		path:     path,
-		readOnly: flags&OPEN_READONLY != 0,
-	}
-}
-
-var _ blockingSharedMemory = &vfsShm{}
-
-type vfsShm struct {
-	*os.File
-	path     string
-	regions  []*util.MappedRegion
-	readOnly bool
-	blocking bool
-	sync.Mutex
-}
-
-func (s *vfsShm) shmOpen() _ErrorCode {
-	if s.File == nil {
-		var flag int
-		if s.readOnly {
-			flag = unix.O_RDONLY
-		} else {
-			flag = unix.O_RDWR
-		}
-		f, err := os.OpenFile(s.path,
-			flag|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
-		if err != nil {
-			return _CANTOPEN
-		}
-		s.File = f
-	}
-
-	// Dead man's switch.
-	if lock, rc := osTestLock(s.File, _SHM_DMS, 1); rc != _OK {
-		return _IOERR_LOCK
-	} else if lock == unix.F_WRLCK {
-		return _BUSY
-	} else if lock == unix.F_UNLCK {
-		if s.readOnly {
-			return _READONLY_CANTINIT
-		}
-		// Do not use a blocking lock here.
-		// If the lock cannot be obtained immediately,
-		// it means some other connection is truncating the file.
-		// And after it has done so, it will not release its lock,
-		// but only downgrade it to a shared lock.
-		// So no point in blocking here.
-		// The call below to obtain the shared DMS lock may use a blocking lock.
-		if rc := osWriteLock(s.File, _SHM_DMS, 1, 0); rc != _OK {
-			return rc
-		}
-		if err := s.Truncate(0); err != nil {
-			return _IOERR_SHMOPEN
-		}
-	}
-	if rc := osReadLock(s.File, _SHM_DMS, 1, time.Millisecond); rc != _OK {
-		return rc
-	}
-	return _OK
-}
-
-func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
-	// Ensure size is a multiple of the OS page size.
-	if int(size)&(unix.Getpagesize()-1) != 0 {
-		return 0, _IOERR_SHMMAP
-	}
-
-	if rc := s.shmOpen(); rc != _OK {
-		return 0, rc
-	}
-
-	// Check if file is big enough.
-	o, err := s.Seek(0, io.SeekEnd)
-	if err != nil {
-		return 0, _IOERR_SHMSIZE
-	}
-	if n := (int64(id) + 1) * int64(size); n > o {
-		if !extend {
-			return 0, _OK
-		}
-		err := osAllocate(s.File, n)
-		if err != nil {
-			return 0, _IOERR_SHMSIZE
-		}
-	}
-
-	var prot int
-	if s.readOnly {
-		prot = unix.PROT_READ
-	} else {
-		prot = unix.PROT_READ | unix.PROT_WRITE
-	}
-	r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size, prot)
-	if err != nil {
-		return 0, _IOERR_SHMMAP
-	}
-	s.regions = append(s.regions, r)
-	if s.readOnly {
-		return r.Ptr, _READONLY
-	}
-	return r.Ptr, _OK
-}
-
-func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
-	// Argument check.
-	if n <= 0 || offset < 0 || offset+n > _SHM_NLOCK {
-		panic(util.AssertErr())
-	}
-	switch flags {
-	case
-		_SHM_LOCK | _SHM_SHARED,
-		_SHM_LOCK | _SHM_EXCLUSIVE,
-		_SHM_UNLOCK | _SHM_SHARED,
-		_SHM_UNLOCK | _SHM_EXCLUSIVE:
-		//
-	default:
-		panic(util.AssertErr())
-	}
-	if n != 1 && flags&_SHM_EXCLUSIVE == 0 {
-		panic(util.AssertErr())
-	}
-
-	var timeout time.Duration
-	if s.blocking {
-		timeout = time.Millisecond
-	}
-
-	switch {
-	case flags&_SHM_UNLOCK != 0:
-		return osUnlock(s.File, _SHM_BASE+int64(offset), int64(n))
-	case flags&_SHM_SHARED != 0:
-		return osReadLock(s.File, _SHM_BASE+int64(offset), int64(n), timeout)
-	case flags&_SHM_EXCLUSIVE != 0:
-		return osWriteLock(s.File, _SHM_BASE+int64(offset), int64(n), timeout)
-	default:
-		panic(util.AssertErr())
-	}
-}
-
-func (s *vfsShm) shmUnmap(delete bool) {
-	if s.File == nil {
-		return
-	}
-
-	// Unmap regions.
-	for _, r := range s.regions {
-		r.Unmap()
-	}
-	clear(s.regions)
-	s.regions = s.regions[:0]
-
-	// Close the file.
-	if delete {
-		os.Remove(s.path)
-	}
-	s.Close()
-	s.File = nil
-}
-
-func (s *vfsShm) shmBarrier() {
-	s.Lock()
-	//lint:ignore SA2001 memory barrier.
-	s.Unlock()
-}
-
-func (s *vfsShm) shmEnableBlocking(block bool) {
-	s.blocking = block
+	return &vfsShm{path: path}
 }

vfs/shm_bsd.go

@@ -1,4 +1,4 @@
-//go:build (freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_noshm || sqlite3_nosys)
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
 
 package vfs
 
@@ -14,44 +14,14 @@ import (
 	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
-// SupportsSharedMemory is false on platforms that do not support shared memory.
-// To use [WAL without shared-memory], you need to set [EXCLUSIVE locking mode].
-//
-// [WAL without shared-memory]: https://sqlite.org/wal.html#noshm
-// [EXCLUSIVE locking mode]: https://sqlite.org/pragma.html#pragma_locking_mode
-const SupportsSharedMemory = true
-
-const _SHM_NLOCK = 8
-
-func (f *vfsFile) SharedMemory() SharedMemory { return f.shm }
-
-// NewSharedMemory returns a shared-memory WAL-index
-// backed by a file with the given path.
-// It will return nil if shared-memory is not supported,
-// or not appropriate for the given flags.
-// Only [OPEN_MAIN_DB] databases may need a WAL-index.
-// You must ensure all concurrent accesses to a database
-// use shared-memory instances created with the same path.
-func NewSharedMemory(path string, flags OpenFlag) SharedMemory {
-	if flags&OPEN_MAIN_DB == 0 || flags&(OPEN_DELETEONCLOSE|OPEN_MEMORY) != 0 {
-		return nil
-	}
-	return &vfsShm{
-		path:     path,
-		readOnly: flags&OPEN_READONLY != 0,
-	}
-}
-
 type vfsShmFile struct {
 	*os.File
 	info os.FileInfo
 
-	// +checklocks:vfsShmFilesMtx
-	refs int
+	refs int // +checklocks:vfsShmFilesMtx
 
-	// +checklocks:lockMtx
-	lock    [_SHM_NLOCK]int16
-	lockMtx sync.Mutex
+	lock [_SHM_NLOCK]int16 // +checklocks:Mutex
+	sync.Mutex
 }
 
 var (
@@ -62,10 +32,9 @@ var (
 
 type vfsShm struct {
 	*vfsShmFile
-	path     string
-	lock     [_SHM_NLOCK]bool
-	regions  []*util.MappedRegion
-	readOnly bool
+	path    string
+	lock    [_SHM_NLOCK]bool
+	regions []*util.MappedRegion
 }
 
 func (s *vfsShm) Close() error {
@@ -80,7 +49,7 @@ func (s *vfsShm) Close() error {
 	s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
 
 	// Decrease reference count.
-	if s.vfsShmFile.refs > 1 {
+	if s.vfsShmFile.refs > 0 {
 		s.vfsShmFile.refs--
 		s.vfsShmFile = nil
 		return nil
@@ -97,7 +66,7 @@ func (s *vfsShm) Close() error {
 	panic(util.AssertErr())
 }
 
-func (s *vfsShm) shmOpen() (rc _ErrorCode) {
+func (s *vfsShm) shmOpen() _ErrorCode {
 	if s.vfsShmFile != nil {
 		return _OK
 	}
@@ -128,34 +97,29 @@ func (s *vfsShm) shmOpen() (rc _ErrorCode) {
 		}
 	}
 
-	// Lock and truncate the file, if not readonly.
+	// Lock and truncate the file.
 	// The lock is only released by closing the file.
-	if s.readOnly {
-		rc = _READONLY_CANTINIT
-	} else {
-		if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
-			return rc
-		}
-		if err := f.Truncate(0); err != nil {
-			return _IOERR_SHMOPEN
-		}
+	if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
+		return rc
+	}
+	if err := f.Truncate(0); err != nil {
+		return _IOERR_SHMOPEN
 	}
 
 	// Add the new shared file.
 	s.vfsShmFile = &vfsShmFile{
 		File: f,
 		info: fi,
-		refs: 1,
 	}
 	f = nil // Don't close the file.
 	for i, g := range vfsShmFiles {
 		if g == nil {
 			vfsShmFiles[i] = s.vfsShmFile
-			return rc
+			return _OK
 		}
 	}
 	vfsShmFiles = append(vfsShmFiles, s.vfsShmFile)
-	return rc
+	return _OK
 }
 
 func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
@@ -177,32 +141,22 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		if !extend {
 			return 0, _OK
 		}
-		err := osAllocate(s.File, n)
-		if err != nil {
+		if osAllocate(s.File, n) != nil {
 			return 0, _IOERR_SHMSIZE
 		}
 	}
 
-	var prot int
-	if s.readOnly {
-		prot = unix.PROT_READ
-	} else {
-		prot = unix.PROT_READ | unix.PROT_WRITE
-	}
-	r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size, prot)
+	r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size, false)
 	if err != nil {
 		return 0, _IOERR_SHMMAP
 	}
 	s.regions = append(s.regions, r)
-	if s.readOnly {
-		return r.Ptr, _READONLY
-	}
 	return r.Ptr, _OK
 }
 
 func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
-	s.lockMtx.Lock()
-	defer s.lockMtx.Unlock()
+	s.Lock()
+	defer s.Unlock()
 
 	switch {
 	case flags&_SHM_UNLOCK != 0:
@@ -224,7 +178,7 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 			if s.lock[i] {
 				panic(util.AssertErr())
 			}
-			if s.vfsShmFile.lock[i] < 0 {
+			if s.vfsShmFile.lock[i]+1 <= 0 {
 				return _BUSY
 			}
 		}
@@ -261,8 +215,7 @@ func (s *vfsShm) shmUnmap(delete bool) {
 	for _, r := range s.regions {
 		r.Unmap()
 	}
-	clear(s.regions)
-	s.regions = s.regions[:0]
+	s.regions = nil
 
 	// Close the file.
 	if delete {
@@ -272,7 +225,7 @@ func (s *vfsShm) shmUnmap(delete bool) {
 }
 
 func (s *vfsShm) shmBarrier() {
-	s.lockMtx.Lock()
+	s.Lock()
 	//lint:ignore SA2001 memory barrier.
-	s.lockMtx.Unlock()
+	s.Unlock()
 }

vfs/shm_copy.go

@@ -0,0 +1,84 @@
+//go:build (windows && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_dotlk
+
+package vfs
+
+import (
+	"unsafe"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+)
+
+const (
+	_WALINDEX_HDR_SIZE = 136
+	_WALINDEX_PGSZ     = 32768
+)
+
+// This looks like a safe way of keeping the WAL-index in sync.
+//
+// The WAL-index file starts with a header,
+// and the index doesn't meaningfully change if the header doesn't change.
+//
+// The header starts with two 48 byte, checksummed, copies of the same information,
+// which are accessed independently between memory barriers.
+// The checkpoint information that follows uses 4 byte aligned words.
+//
+// Finally, we have the WAL-index hash tables,
+// which are only modified holding the exclusive WAL_WRITE_LOCK.
+//
+// Since all the data is either redundant+checksummed,
+// 4 byte aligned, or modified under an exclusive lock,
+// the copies below should correctly keep copies in sync.
+//
+// https://sqlite.org/walformat.html#the_wal_index_file_format
+
+func (s *vfsShm) shmAcquire() {
+	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], s.shared[0][:]) {
+		return
+	}
+	// Copies modified words from shared to private memory.
+	for id, p := range s.ptrs {
+		shared := shmPage(s.shared[id][:])
+		shadow := shmPage(s.shadow[id][:])
+		privat := shmPage(util.View(s.mod, p, _WALINDEX_PGSZ))
+		for i, shared := range shared {
+			if shadow[i] != shared {
+				shadow[i] = shared
+				privat[i] = shared
+			}
+		}
+	}
+}
+
+func (s *vfsShm) shmRelease() {
+	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE)) {
+		return
+	}
+	// Copies modified words from private to shared memory.
+	for id, p := range s.ptrs {
+		shared := shmPage(s.shared[id][:])
+		shadow := shmPage(s.shadow[id][:])
+		privat := shmPage(util.View(s.mod, p, _WALINDEX_PGSZ))
+		for i, privat := range privat {
+			if shadow[i] != privat {
+				shadow[i] = privat
+				shared[i] = privat
+			}
+		}
+	}
+}
+
+func (s *vfsShm) shmBarrier() {
+	s.Lock()
+	s.shmAcquire()
+	s.shmRelease()
+	s.Unlock()
+}
+
+func shmPage(s []byte) *[_WALINDEX_PGSZ / 4]uint32 {
+	p := (*uint32)(unsafe.Pointer(unsafe.SliceData(s)))
+	return (*[_WALINDEX_PGSZ / 4]uint32)(unsafe.Slice(p, _WALINDEX_PGSZ/4))
+}
+
+func shmUnmodified(v1, v2 []byte) bool {
+	return *(*[_WALINDEX_HDR_SIZE]byte)(v1[:]) == *(*[_WALINDEX_HDR_SIZE]byte)(v2[:])
+}

vfs/shm_dotlk.go

@@ -0,0 +1,220 @@
+//go:build sqlite3_dotlk
+
+package vfs
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"os"
+	"sync"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+	"github.com/tetratelabs/wazero/api"
+)
+
+type vfsShmBuffer struct {
+	shared [][_WALINDEX_PGSZ]byte
+	refs   int // +checklocks:vfsShmBuffersMtx
+
+	lock [_SHM_NLOCK]int16 // +checklocks:Mutex
+	sync.Mutex
+}
+
+var (
+	// +checklocks:vfsShmBuffersMtx
+	vfsShmBuffers    = map[string]*vfsShmBuffer{}
+	vfsShmBuffersMtx sync.Mutex
+)
+
+type vfsShm struct {
+	*vfsShmBuffer
+	mod    api.Module
+	alloc  api.Function
+	free   api.Function
+	path   string
+	shadow [][_WALINDEX_PGSZ]byte
+	ptrs   []uint32
+	stack  [1]uint64
+	lock   [_SHM_NLOCK]bool
+}
+
+func (s *vfsShm) Close() error {
+	if s.vfsShmBuffer == nil {
+		return nil
+	}
+
+	vfsShmBuffersMtx.Lock()
+	defer vfsShmBuffersMtx.Unlock()
+
+	// Unlock everything.
+	s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
+
+	// Decrease reference count.
+	if s.vfsShmBuffer.refs > 0 {
+		s.vfsShmBuffer.refs--
+		s.vfsShmBuffer = nil
+		return nil
+	}
+
+	err := os.Remove(s.path)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return _IOERR_UNLOCK
+	}
+	delete(vfsShmBuffers, s.path)
+	s.vfsShmBuffer = nil
+	return nil
+}
+
+func (s *vfsShm) shmOpen() _ErrorCode {
+	if s.vfsShmBuffer != nil {
+		return _OK
+	}
+
+	vfsShmBuffersMtx.Lock()
+	defer vfsShmBuffersMtx.Unlock()
+
+	// Find a shared buffer, increase the reference count.
+	if g, ok := vfsShmBuffers[s.path]; ok {
+		s.vfsShmBuffer = g
+		g.refs++
+		return _OK
+	}
+
+	// Create a directory on disk to ensure only this process
+	// uses this path to register a shared memory.
+	err := os.Mkdir(s.path, 0777)
+	if errors.Is(err, fs.ErrExist) {
+		return _BUSY
+	}
+	if err != nil {
+		return _IOERR_LOCK
+	}
+
+	// Add the new shared buffer.
+	s.vfsShmBuffer = &vfsShmBuffer{}
+	vfsShmBuffers[s.path] = s.vfsShmBuffer
+	return _OK
+}
+
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+	if size != _WALINDEX_PGSZ {
+		return 0, _IOERR_SHMMAP
+	}
+	if s.mod == nil {
+		s.mod = mod
+		s.free = mod.ExportedFunction("sqlite3_free")
+		s.alloc = mod.ExportedFunction("sqlite3_malloc64")
+	}
+	if rc := s.shmOpen(); rc != _OK {
+		return 0, rc
+	}
+
+	s.Lock()
+	defer s.Unlock()
+	defer s.shmAcquire()
+
+	if int(id) >= len(s.shared) {
+		if !extend {
+			return 0, _OK
+		}
+		s.shared = append(s.shared, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shared)+1)...)
+	}
+
+	if int(id) >= len(s.shadow) {
+		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
+	}
+
+	for int(id) >= len(s.ptrs) {
+		s.stack[0] = uint64(size)
+		if err := s.alloc.CallWithStack(ctx, s.stack[:]); err != nil {
+			panic(err)
+		}
+		if s.stack[0] == 0 {
+			panic(util.OOMErr)
+		}
+		clear(util.View(s.mod, uint32(s.stack[0]), _WALINDEX_PGSZ))
+		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
+	}
+
+	return s.ptrs[id], _OK
+}
+
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+	s.Lock()
+	defer s.Unlock()
+
+	switch {
+	case flags&_SHM_LOCK != 0:
+		defer s.shmAcquire()
+	case flags&_SHM_EXCLUSIVE != 0:
+		s.shmRelease()
+	}
+
+	switch {
+	case flags&_SHM_UNLOCK != 0:
+		for i := offset; i < offset+n; i++ {
+			if s.lock[i] {
+				if s.vfsShmBuffer.lock[i] == 0 {
+					panic(util.AssertErr())
+				}
+				if s.vfsShmBuffer.lock[i] <= 0 {
+					s.vfsShmBuffer.lock[i] = 0
+				} else {
+					s.vfsShmBuffer.lock[i]--
+				}
+				s.lock[i] = false
+			}
+		}
+	case flags&_SHM_SHARED != 0:
+		for i := offset; i < offset+n; i++ {
+			if s.lock[i] {
+				panic(util.AssertErr())
+			}
+			if s.vfsShmBuffer.lock[i]+1 <= 0 {
+				return _BUSY
+			}
+		}
+		for i := offset; i < offset+n; i++ {
+			s.vfsShmBuffer.lock[i]++
+			s.lock[i] = true
+		}
+	case flags&_SHM_EXCLUSIVE != 0:
+		for i := offset; i < offset+n; i++ {
+			if s.lock[i] {
+				panic(util.AssertErr())
+			}
+			if s.vfsShmBuffer.lock[i] != 0 {
+				return _BUSY
+			}
+		}
+		for i := offset; i < offset+n; i++ {
+			s.vfsShmBuffer.lock[i] = -1
+			s.lock[i] = true
+		}
+	default:
+		panic(util.AssertErr())
+	}
+
+	return _OK
+}
+
+func (s *vfsShm) shmUnmap(delete bool) {
+	if s.vfsShmBuffer == nil {
+		return
+	}
+	defer s.Close()
+
+	s.Lock()
+	s.shmRelease()
+	defer s.Unlock()
+
+	for _, p := range s.ptrs {
+		s.stack[0] = uint64(p)
+		if err := s.free.CallWithStack(context.Background(), s.stack[:]); err != nil {
+			panic(err)
+		}
+	}
+	s.ptrs = nil
+	s.shadow = nil
+}

vfs/shm_ofd.go

@@ -0,0 +1,168 @@
+//go:build (linux || darwin) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_flock || sqlite3_dotlk || sqlite3_nosys)
+
+package vfs
+
+import (
+	"context"
+	"io"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/tetratelabs/wazero/api"
+	"golang.org/x/sys/unix"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+)
+
+type vfsShm struct {
+	*os.File
+	path     string
+	regions  []*util.MappedRegion
+	readOnly bool
+	blocking bool
+	sync.Mutex
+}
+
+var _ blockingSharedMemory = &vfsShm{}
+
+func (s *vfsShm) shmOpen() _ErrorCode {
+	if s.File == nil {
+		f, err := os.OpenFile(s.path,
+			unix.O_RDWR|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
+		if err != nil {
+			f, err = os.OpenFile(s.path,
+				unix.O_RDONLY|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
+			s.readOnly = true
+		}
+		if err != nil {
+			return _CANTOPEN
+		}
+		s.File = f
+	}
+
+	// Dead man's switch.
+	if lock, rc := osTestLock(s.File, _SHM_DMS, 1); rc != _OK {
+		return _IOERR_LOCK
+	} else if lock == unix.F_WRLCK {
+		return _BUSY
+	} else if lock == unix.F_UNLCK {
+		if s.readOnly {
+			return _READONLY_CANTINIT
+		}
+		// Do not use a blocking lock here.
+		// If the lock cannot be obtained immediately,
+		// it means some other connection is truncating the file.
+		// And after it has done so, it will not release its lock,
+		// but only downgrade it to a shared lock.
+		// So no point in blocking here.
+		// The call below to obtain the shared DMS lock may use a blocking lock.
+		if rc := osWriteLock(s.File, _SHM_DMS, 1, 0); rc != _OK {
+			return rc
+		}
+		if err := s.Truncate(0); err != nil {
+			return _IOERR_SHMOPEN
+		}
+	}
+	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+}
+
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+	// Ensure size is a multiple of the OS page size.
+	if int(size)&(unix.Getpagesize()-1) != 0 {
+		return 0, _IOERR_SHMMAP
+	}
+
+	if rc := s.shmOpen(); rc != _OK {
+		return 0, rc
+	}
+
+	// Check if file is big enough.
+	o, err := s.Seek(0, io.SeekEnd)
+	if err != nil {
+		return 0, _IOERR_SHMSIZE
+	}
+	if n := (int64(id) + 1) * int64(size); n > o {
+		if !extend {
+			return 0, _OK
+		}
+		if s.readOnly || osAllocate(s.File, n) != nil {
+			return 0, _IOERR_SHMSIZE
+		}
+	}
+
+	r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size, s.readOnly)
+	if err != nil {
+		return 0, _IOERR_SHMMAP
+	}
+	s.regions = append(s.regions, r)
+	if s.readOnly {
+		return r.Ptr, _READONLY
+	}
+	return r.Ptr, _OK
+}
+
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+	// Argument check.
+	if n <= 0 || offset < 0 || offset+n > _SHM_NLOCK {
+		panic(util.AssertErr())
+	}
+	switch flags {
+	case
+		_SHM_LOCK | _SHM_SHARED,
+		_SHM_LOCK | _SHM_EXCLUSIVE,
+		_SHM_UNLOCK | _SHM_SHARED,
+		_SHM_UNLOCK | _SHM_EXCLUSIVE:
+		//
+	default:
+		panic(util.AssertErr())
+	}
+	if n != 1 && flags&_SHM_EXCLUSIVE == 0 {
+		panic(util.AssertErr())
+	}
+
+	var timeout time.Duration
+	if s.blocking {
+		timeout = time.Millisecond
+	}
+
+	switch {
+	case flags&_SHM_UNLOCK != 0:
+		return osUnlock(s.File, _SHM_BASE+int64(offset), int64(n))
+	case flags&_SHM_SHARED != 0:
+		return osReadLock(s.File, _SHM_BASE+int64(offset), int64(n), timeout)
+	case flags&_SHM_EXCLUSIVE != 0:
+		return osWriteLock(s.File, _SHM_BASE+int64(offset), int64(n), timeout)
+	default:
+		panic(util.AssertErr())
+	}
+}
+
+func (s *vfsShm) shmUnmap(delete bool) {
+	if s.File == nil {
+		return
+	}
+
+	// Unmap regions.
+	for _, r := range s.regions {
+		r.Unmap()
+	}
+	s.regions = nil
+
+	// Close the file.
+	if delete {
+		os.Remove(s.path)
+	}
+	s.Close()
+	s.File = nil
+}
+
+func (s *vfsShm) shmBarrier() {
+	s.Lock()
+	//lint:ignore SA2001 memory barrier.
+	s.Unlock()
+}
+
+func (s *vfsShm) shmEnableBlocking(block bool) {
+	s.blocking = block
+}

vfs/shm_other.go

@@ -1,4 +1,4 @@
-//go:build !(darwin || linux || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) || !(386 || arm || amd64 || arm64 || riscv64 || ppc64le) || sqlite3_noshm || sqlite3_nosys
+//go:build !(((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 

vfs/shm_windows.go

@@ -0,0 +1,183 @@
+//go:build (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_nosys)
+
+package vfs
+
+import (
+	"context"
+	"io"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/tetratelabs/wazero/api"
+	"golang.org/x/sys/windows"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+	"github.com/ncruces/go-sqlite3/util/osutil"
+)
+
+type vfsShm struct {
+	*os.File
+	mod      api.Module
+	alloc    api.Function
+	free     api.Function
+	path     string
+	regions  []*util.MappedRegion
+	shared   [][]byte
+	shadow   [][_WALINDEX_PGSZ]byte
+	ptrs     []uint32
+	stack    [1]uint64
+	blocking bool
+	sync.Mutex
+}
+
+var _ blockingSharedMemory = &vfsShm{}
+
+func (s *vfsShm) Close() error {
+	// Unmap regions.
+	for _, r := range s.regions {
+		r.Unmap()
+	}
+	s.regions = nil
+
+	// Close the file.
+	return s.File.Close()
+}
+
+func (s *vfsShm) shmOpen() _ErrorCode {
+	if s.File == nil {
+		f, err := osutil.OpenFile(s.path, os.O_RDWR|os.O_CREATE, 0666)
+		if err != nil {
+			return _CANTOPEN
+		}
+		s.File = f
+	}
+
+	// Dead man's switch.
+	if rc := osWriteLock(s.File, _SHM_DMS, 1, 0); rc == _OK {
+		err := s.Truncate(0)
+		osUnlock(s.File, _SHM_DMS, 1)
+		if err != nil {
+			return _IOERR_SHMOPEN
+		}
+	}
+	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+}
+
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+	// Ensure size is a multiple of the OS page size.
+	if size != _WALINDEX_PGSZ || (windows.Getpagesize()-1)&_WALINDEX_PGSZ != 0 {
+		return 0, _IOERR_SHMMAP
+	}
+	if s.mod == nil {
+		s.mod = mod
+		s.free = mod.ExportedFunction("sqlite3_free")
+		s.alloc = mod.ExportedFunction("sqlite3_malloc64")
+	}
+	if rc := s.shmOpen(); rc != _OK {
+		return 0, rc
+	}
+
+	defer s.shmAcquire()
+
+	// Check if file is big enough.
+	o, err := s.Seek(0, io.SeekEnd)
+	if err != nil {
+		return 0, _IOERR_SHMSIZE
+	}
+	if n := (int64(id) + 1) * int64(size); n > o {
+		if !extend {
+			return 0, _OK
+		}
+		if osAllocate(s.File, n) != nil {
+			return 0, _IOERR_SHMSIZE
+		}
+	}
+
+	// Map the region into memory.
+	r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size)
+	if err != nil {
+		return 0, _IOERR_SHMMAP
+	}
+	s.regions = append(s.regions, r)
+
+	if int(id) >= len(s.shared) {
+		s.shared = append(s.shared, make([][]byte, int(id)-len(s.shared)+1)...)
+	}
+	s.shared[id] = r.Data
+
+	// Allocate shadow memory.
+	if int(id) >= len(s.shadow) {
+		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
+	}
+
+	// Allocate local memory.
+	for int(id) >= len(s.ptrs) {
+		s.stack[0] = uint64(size)
+		if err := s.alloc.CallWithStack(ctx, s.stack[:]); err != nil {
+			panic(err)
+		}
+		if s.stack[0] == 0 {
+			panic(util.OOMErr)
+		}
+		clear(util.View(s.mod, uint32(s.stack[0]), _WALINDEX_PGSZ))
+		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
+	}
+
+	return s.ptrs[id], _OK
+}
+
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+	switch {
+	case flags&_SHM_LOCK != 0:
+		defer s.shmAcquire()
+	case flags&_SHM_EXCLUSIVE != 0:
+		s.shmRelease()
+	}
+
+	var timeout time.Duration
+	if s.blocking {
+		timeout = time.Millisecond
+	}
+
+	switch {
+	case flags&_SHM_UNLOCK != 0:
+		return osUnlock(s.File, _SHM_BASE+uint32(offset), uint32(n))
+	case flags&_SHM_SHARED != 0:
+		return osReadLock(s.File, _SHM_BASE+uint32(offset), uint32(n), timeout)
+	case flags&_SHM_EXCLUSIVE != 0:
+		return osWriteLock(s.File, _SHM_BASE+uint32(offset), uint32(n), timeout)
+	default:
+		panic(util.AssertErr())
+	}
+}
+
+func (s *vfsShm) shmUnmap(delete bool) {
+	if s.File == nil {
+		return
+	}
+
+	s.shmRelease()
+
+	// Free local memory.
+	for _, p := range s.ptrs {
+		s.stack[0] = uint64(p)
+		if err := s.free.CallWithStack(context.Background(), s.stack[:]); err != nil {
+			panic(err)
+		}
+	}
+	s.ptrs = nil
+	s.shadow = nil
+	s.shared = nil
+
+	// Close the file.
+	s.Close()
+	s.File = nil
+	if delete {
+		os.Remove(s.path)
+	}
+}
+
+func (s *vfsShm) shmEnableBlocking(block bool) {
+	s.blocking = block
+}

vfs/tests/mptest/mptest_test.go

@@ -145,9 +145,6 @@ func Test_crash01(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping in short mode")
 	}
-	if os.Getenv("CI") != "" {
-		t.Skip("skipping in CI")
-	}
 	if !vfs.SupportsFileLocking {
 		t.Skip("skipping without locks")
 	}
@@ -212,9 +209,6 @@ func Test_crash01_wal(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping in short mode")
 	}
-	if os.Getenv("CI") != "" {
-		t.Skip("skipping in CI")
-	}
 	if !vfs.SupportsSharedMemory {
 		t.Skip("skipping without shared memory")
 	}

vfs/tests/mptest/testdata/exports.txt

@@ -1,5 +1,5 @@
 aligned_alloc
-free
-malloc
 sqlite3_database_file_object
+sqlite3_free
+sqlite3_malloc64
 sqlite3_uri_key

vfs/tests/mptest/testdata/mptest.wasm.bz2

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:5c69a9b1c88bc735797d81f9ba979a2683f66f8b2fe88106dcbd1cdb0bb26043
-size 480731
+oid sha256:4a2ed4f7fe323843e78c59a23e0bd078d807745a3e6276a9862ff08bb7bdac18
+size 480769

vfs/tests/speedtest1/testdata/exports.txt

@@ -1,5 +1,5 @@
 aligned_alloc
-free
-malloc
 sqlite3_database_file_object
+sqlite3_free
+sqlite3_malloc64
 sqlite3_uri_key

vfs/tests/speedtest1/testdata/speedtest1.wasm.bz2

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:a2f414d7540e31733b6c2f1cbfb2f8d39506215487a1b73aa03f80d8a2fe371a
-size 493518
+oid sha256:98abb49f1b6acf5398c08556571d44acdc7258484e510b3f8c7a19ee42b5821c
+size 493373