feat: VipsTarget integration with io.WriteCloser (#47)

* prepare vips target

* build: update generated vips package

* prepare vips target

* build: update generated vips package

* prepare vips target

* build: update generated vips package

* tweak mime method ordering

* tweak mime method ordering

* add test case

* Update streaming wordings

Author: cshum

README.md

@@ -1,10 +1,10 @@
 # vipsgen
 
-[![CI](https://github.com/cshum/vipsgen/actions/workflows/ci.yml/badge.svg)](https://github.com/cshum/vipsgen/actions/workflows/ci.yml)
 [![Go Reference](https://pkg.go.dev/badge/github.com/cshum/vipsgen/vips.svg)](https://pkg.go.dev/github.com/cshum/vipsgen/vips)
+[![CI](https://github.com/cshum/vipsgen/actions/workflows/ci.yml/badge.svg)](https://github.com/cshum/vipsgen/actions/workflows/ci.yml)
 [![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/cshum/vipsgen)](https://github.com/cshum/vipsgen/releases)
 
-vipsgen is a Go binding generator for [libvips](https://www.libvips.org/) - a fast and efficient image processing library.
+vipsgen is a Go binding generator for [libvips](https://github.com/libvips/libvips) - a fast and efficient image processing library.
 
 Existing Go libvips bindings rely on manually written code that is often incomplete, error-prone, and difficult to maintain as libvips evolves.
 vipsgen solves this by generating type-safe, robust, and fully documented Go bindings using GObject introspection.
@@ -19,7 +19,7 @@ You can use vipsgen in two ways:
 - **Comprehensive**: Bindings for around [300 libvips operations](https://www.libvips.org/API/current/func-list.html)
 - **Type-Safe**: Proper Go types for all libvips C enums and structs
 - **Idiomatic**: Clean Go APIs that feel natural to use
-- **Streaming**: Includes `VipsSource` integration with `io.ReadCloser` for [streaming](https://www.libvips.org/2019/11/29/True-streaming-for-libvips.html)
+- **Streaming**: `VipsSource` and `VipsTarget` integration with Go `io.Reader` and `io.Writer` for [streaming](https://www.libvips.org/2019/11/29/True-streaming-for-libvips.html)
 
 ## Quick Start
 

internal/generator/templatefunc.go

@@ -406,7 +406,7 @@ func generateFunctionCallArgs(op introspection.Operation, withOptions bool) stri
 				callArgs = append(callArgs, argStr)
 				continue
 			}
-			if arg.IsSource {
+			if arg.IsSource || arg.IsTarget {
 				callArgs = append(callArgs, arg.GoName)
 			} else if arg.GoType == "string" {
 				argStr = "c" + arg.GoName
@@ -565,6 +565,8 @@ func generateImageMethodBody(op introspection.Operation) string {
 	for _, arg := range methodArgs {
 		if arg.GoType == "*C.VipsImage" {
 			callArgs = append(callArgs, fmt.Sprintf("%s.image", arg.GoName))
+		} else if arg.IsTarget {
+			callArgs = append(callArgs, fmt.Sprintf("%s.target", arg.GoName))
 		} else if arg.GoType == "[]*C.VipsImage" {
 			callArgs = append(callArgs, fmt.Sprintf("convertImagesToVipsImages(%s)", arg.GoName))
 		} else {
@@ -1089,6 +1091,8 @@ func generateImageMethodParams(op introspection.Operation) string {
 			paramType = "[]*Image"
 		} else if arg.CType == "void*" {
 			paramType = "[]byte"
+		} else if arg.IsTarget {
+			paramType = "*Target"
 		} else {
 			paramType = arg.GoType
 		}
@@ -1355,9 +1359,12 @@ func generateCFunctionImplementation(op introspection.Operation) string {
 			if i > 0 {
 				result.WriteString(", ")
 			}
-			// Add type casting for VipsSourceCustom
 			if arg.IsSource {
+				// Add type casting for VipsSourceCustom
 				result.WriteString("(VipsSource*) " + arg.Name)
+			} else if arg.IsTarget {
+				// Add type casting for VipsTargetCustom
+				result.WriteString("(VipsTarget*) " + arg.Name)
 			} else {
 				result.WriteString(arg.Name)
 			}
@@ -1470,6 +1477,9 @@ func generateCFunctionImplementation(op introspection.Operation) string {
 			} else if arg.IsSource {
 				allParamsList = append(allParamsList,
 					fmt.Sprintf("vips_object_set(VIPS_OBJECT(operation), \"%s\", (VipsSource*)%s, NULL)", arg.Name, arg.Name))
+			} else if arg.IsTarget {
+				allParamsList = append(allParamsList,
+					fmt.Sprintf("vips_object_set(VIPS_OBJECT(operation), \"%s\", (VipsTarget*)%s, NULL)", arg.Name, arg.Name))
 			} else if (arg.Name == "buf" || arg.Name == "buffer") && isBufferLoadOperation {
 				// For buffer load operations, set the VipsBlob as the "buffer" property
 				allParamsList = append(allParamsList,
@@ -1526,6 +1536,10 @@ func generateCFunctionImplementation(op introspection.Operation) string {
 				// Handle source parameters
 				allParamsList = append(allParamsList,
 					fmt.Sprintf("vipsgen_set_source(operation, \"%s\", %s)", opt.Name, opt.Name))
+			} else if opt.IsTarget {
+				// Handle target parameters
+				allParamsList = append(allParamsList,
+					fmt.Sprintf("vipsgen_set_target(operation, \"%s\", %s)", opt.Name, opt.Name))
 			} else if opt.GoType == "int" {
 				allParamsList = append(allParamsList,
 					fmt.Sprintf("vipsgen_set_int(operation, \"%s\", %s)", opt.Name, opt.Name))

internal/introspection/operation.go

@@ -43,6 +43,7 @@ type Argument struct {
 	IsOutput     bool
 	IsOutputN    bool
 	IsSource     bool
+	IsTarget     bool
 	IsImage      bool
 	IsBuffer     bool
 	IsArray      bool
@@ -129,8 +130,7 @@ func (v *Introspection) DiscoverOperations() []Operation {
 			op.HasOneImageOutput = false
 		}
 
-		if strings.Contains(op.Name, "_target") ||
-			strings.Contains(op.Name, "_mime") ||
+		if strings.Contains(op.Name, "_mime") ||
 			strings.Contains(op.Name, "fitsload_source") {
 			log.Printf("Excluded operation: vips_%s \n", op.Name)
 			excludedCount++
@@ -202,6 +202,7 @@ func (v *Introspection) DiscoverOperationArguments(opName string) ([]Argument, e
 		isBuffer := int(arg.is_buffer) != 0
 		isArray := int(arg.is_array) != 0
 		isSource := cTypeCheck(arg.type_val, "VipsSource")
+		isTarget := cTypeCheck(arg.type_val, "VipsTarget")
 
 		// Create the Go argument structure
 		goArg := Argument{
@@ -215,6 +216,7 @@ func (v *Introspection) DiscoverOperationArguments(opName string) ([]Argument, e
 			IsBuffer:    isBuffer,
 			IsArray:     isArray,
 			IsSource:    isSource,
+			IsTarget:    isTarget,
 			Flags:       int(arg.flags),
 		}
 
@@ -492,6 +494,14 @@ func (v *Introspection) mapGTypeToTypes(gtype C.GType, typeName string, isOutput
 		}
 		return "VipsSourceCustom", "*C.VipsSourceCustom", "VipsSourceCustom*"
 	}
+	// Special case for VipsTarget - map to VipsTargetCustom for proper compatibility
+	if cTypeCheck(gtype, "VipsTarget") {
+		// For VipsTarget, we want to use VipsTargetCustom in the bindings
+		if isOutput {
+			return "VipsTargetCustom", "*C.VipsTargetCustom", "VipsTargetCustom**"
+		}
+		return "VipsTargetCustom", "*C.VipsTargetCustom", "VipsTargetCustom*"
+	}
 	// Special case for VipsImage which has a different pointer pattern
 	if cTypeCheck(gtype, "VipsImage") {
 		if isOutput {

internal/templates/callback.go.tmpl

@@ -53,3 +53,24 @@ func goSourceSeek(
 	}
 	return -1
 }
+
+//export goTargetWrite
+func goTargetWrite(
+	ptr unsafe.Pointer, buffer unsafe.Pointer, size C.longlong,
+) C.longlong {
+	target, ok := pointer.Restore(ptr).(*Target)
+	if !ok {
+		return -1
+	}
+	sh := &reflect.SliceHeader{
+		Data: uintptr(buffer),
+		Len:  int(size),
+		Cap:  int(size),
+	}
+	buf := *(*[]byte)(unsafe.Pointer(sh))
+	n, err := target.writer.Write(buf)
+	if err != nil {
+		return -1
+	}
+	return C.longlong(n)
+}

internal/templates/connection.c.tmpl

@@ -12,6 +12,11 @@ static gint64 go_seek(VipsSourceCustom *source_custom, gint64 offset, int whence
   return goSourceSeek(ptr, offset, whence);
 }
 
+static gint64 go_write(VipsTargetCustom *target_custom, void *buffer, gint64 length, void* ptr)
+{
+  return goTargetWrite(ptr, buffer, length);
+}
+
 VipsSourceCustom * create_go_custom_source(void* ptr)
 {
   VipsSourceCustom * source_custom = vips_source_custom_new();
@@ -27,6 +32,17 @@ VipsSourceCustom * create_go_custom_source_with_seek(void* ptr)
   return source_custom;
 }
 
+VipsTargetCustom * create_go_custom_target(void* ptr)
+{
+  VipsTargetCustom * target_custom = vips_target_custom_new();
+  g_signal_connect(target_custom, "write", G_CALLBACK(go_write), ptr);
+  return target_custom;
+}
+
 void clear_source(VipsSourceCustom **source_custom) {
   if (G_IS_OBJECT(*source_custom)) g_clear_object(source_custom);
 }
+
+void clear_target(VipsTargetCustom **target_custom) {
+  if (G_IS_OBJECT(*target_custom)) g_clear_object(target_custom);
+}

internal/templates/connection.go.tmpl

@@ -57,3 +57,41 @@ func (s *Source) Close() {
 		s.lock.Unlock()
 	}
 }
+
+// Target contains a libvips VipsTargetCustom and manages its lifecycle.
+type Target struct {
+	writer io.WriteCloser
+	target *C.VipsTargetCustom
+	ptr    unsafe.Pointer
+	lock   sync.Mutex
+}
+
+// NewTarget creates Target from writer
+func NewTarget(writer io.WriteCloser) *Target {
+	Startup(nil)
+	t := &Target{writer: writer}
+	t.ptr = pointer.Save(t)
+	t.target = C.create_go_custom_target(t.ptr)
+	return t
+}
+
+// Close target
+func (t *Target) Close() {
+	if t == nil {
+		return
+	}
+	t.lock.Lock()
+	if t.ptr != nil {
+		C.clear_target(&t.target)
+		pointer.Unref(t.ptr)
+		t.ptr = nil
+		t.lock.Unlock()
+		if t.writer != nil {
+			_ = t.writer.Close()
+			t.writer = nil
+		}
+		log("vipsgen", LogLevelDebug, fmt.Sprintf("closing target %p", t))
+	} else {
+		t.lock.Unlock()
+	}
+}

internal/templates/connection.h.tmpl

@@ -4,14 +4,16 @@
 #include <vips/vips.h>
 
 extern long long goSourceRead(void*, void *, long long);
-
 extern long long goSourceSeek(void*, long long, int);
+extern long long goTargetWrite(void*, void *, long long);
 
 static gint64 go_read(VipsSourceCustom *source_custom, void *buffer, gint64 length, void* ptr);
-
 static gint64 go_seek(VipsSourceCustom *source_custom, gint64 offset, int whence, void* ptr);
+static gint64 go_write(VipsTargetCustom *target_custom, void *buffer, gint64 length, void* ptr);
 
 VipsSourceCustom * create_go_custom_source(void* ptr);
 VipsSourceCustom * create_go_custom_source_with_seek(void* ptr);
+VipsTargetCustom * create_go_custom_target(void* ptr);
 
 void clear_source(VipsSourceCustom **source_custom);
+void clear_target(VipsTargetCustom **target_custom);

internal/templates/vips.c.tmpl

@@ -99,6 +99,11 @@ int vipsgen_set_source(VipsOperation *operation, const char *name, VipsSource *v
     return 0;
 }
 
+int vipsgen_set_target(VipsOperation *operation, const char *name, VipsTarget *value) {
+    if (value != NULL) { return vips_object_set(VIPS_OBJECT(operation), name, value, NULL); }
+    return 0;
+}
+
 // Generated operations
 {{range .Operations}}
 {{generateCFunctionImplementation .}}

internal/templates/vips.h.tmpl

@@ -9,6 +9,7 @@
 int vipsgen_operation_execute(VipsOperation *operation, ...);
 int vipsgen_operation_save_buffer(VipsOperation *operation, void** buf, size_t* len);
 int vipsgen_set_source(VipsOperation *operation, const char *name, VipsSource *value);
+int vipsgen_set_target(VipsOperation *operation, const char *name, VipsTarget *value);
 int vipsgen_set_int(VipsOperation *operation, const char *name, int value);
 int vipsgen_set_bool(VipsOperation *operation, const char *name, gboolean value);
 int vipsgen_set_double(VipsOperation *operation, const char *name, double value);