Error handling.

context.go

@@ -1,6 +1,7 @@
 package sqlite3
 
 import (
+	"errors"
 	"math"
 	"time"
 
@@ -119,3 +120,37 @@ func (c *Context) resultRFC3339Nano(value time.Time) {
 		uint64(c.handle), uint64(ptr), uint64(len(buf)),
 		uint64(c.c.api.destructor), _UTF8)
 }
+
+// ResultError sets the result of the function an error.
+//
+// https://www.sqlite.org/c3ref/result_blob.html
+func (c *Context) ResultError(err error) {
+	if errors.Is(err, NOMEM) {
+		c.c.call(c.c.api.resultErrorMem, uint64(c.handle))
+		return
+	}
+
+	if errors.Is(err, TOOBIG) {
+		c.c.call(c.c.api.resultErrorBig, uint64(c.handle))
+		return
+	}
+
+	str := err.Error()
+	ptr := c.c.arena.string(str)
+	c.c.call(c.c.api.resultBlob,
+		uint64(c.handle), uint64(ptr), uint64(len(str)))
+
+	var code uint64
+	var ecode ErrorCode
+	var xcode xErrorCode
+	switch {
+	case errors.As(err, &xcode):
+		code = uint64(xcode)
+	case errors.As(err, &ecode):
+		code = uint64(ecode)
+	}
+	if code != 0 {
+		c.c.call(c.c.api.resultErrorCode,
+			uint64(c.handle), uint64(xcode))
+	}
+}

error.go

@@ -68,6 +68,19 @@ func (e *Error) Is(err error) bool {
 	return false
 }
 
+// As converts this error to an [ErrorCode] or [ExtendedErrorCode].
+func (e *Error) As(err any) bool {
+	switch c := err.(type) {
+	case *ErrorCode:
+		*c = e.Code()
+		return true
+	case *ExtendedErrorCode:
+		*c = e.ExtendedCode()
+		return true
+	}
+	return false
+}
+
 // Temporary returns true for [BUSY] errors.
 func (e *Error) Temporary() bool {
 	return e.Code() == BUSY
@@ -104,6 +117,15 @@ func (e ExtendedErrorCode) Is(err error) bool {
 	return ok && c == ErrorCode(e)
 }
 
+// As converts this error to an [ErrorCode].
+func (e ExtendedErrorCode) As(err any) bool {
+	c, ok := err.(*ErrorCode)
+	if ok {
+		*c = ErrorCode(e)
+	}
+	return ok
+}
+
 // Temporary returns true for [BUSY] errors.
 func (e ExtendedErrorCode) Temporary() bool {
 	return ErrorCode(e) == BUSY

error_test.go

@@ -18,22 +18,36 @@ func Test_assertErr(t *testing.T) {
 func TestError(t *testing.T) {
 	t.Parallel()
 
-	err := Error{code: 0x8080}
-	if rc := err.Code(); rc != 0x80 {
-		t.Errorf("got %#x, want 0x80", rc)
+	var ecode ErrorCode
+	var xcode xErrorCode
+	err := &Error{code: 0x8080}
+	if !errors.As(err, &err) {
+		t.Fatal("want true")
 	}
-	if !errors.Is(&err, ErrorCode(0x80)) {
+	if ecode := err.Code(); ecode != 0x80 {
+		t.Errorf("got %#x, want 0x80", uint8(ecode))
+	}
+	if ok := errors.As(err, &ecode); !ok || ecode != ErrorCode(0x80) {
+		t.Errorf("got %#x, want 0x80", uint8(ecode))
+	}
+	if !errors.Is(err, ErrorCode(0x80)) {
 		t.Errorf("want true")
 	}
-	if rc := err.ExtendedCode(); rc != 0x8080 {
-		t.Errorf("got %#x, want 0x8080", rc)
+	if xcode := err.ExtendedCode(); xcode != 0x8080 {
+		t.Errorf("got %#x, want 0x8080", uint16(xcode))
 	}
-	if !errors.Is(&err, ExtendedErrorCode(0x8080)) {
+	if ok := errors.As(err, &xcode); !ok || xcode != xErrorCode(0x8080) {
+		t.Errorf("got %#x, want 0x8080", uint16(xcode))
+	}
+	if !errors.Is(err, xErrorCode(0x8080)) {
 		t.Errorf("want true")
 	}
 	if s := err.Error(); s != "sqlite3: 32896" {
 		t.Errorf("got %q", s)
 	}
+	if ok := errors.As(err.ExtendedCode(), &ecode); !ok || ecode != ErrorCode(0x80) {
+		t.Errorf("got %#x, want 0x80", uint8(ecode))
+	}
 	if !errors.Is(err.ExtendedCode(), ErrorCode(0x80)) {
 		t.Errorf("want true")
 	}