added sliceBuffer built-in

src/objects/o_buffer.c

@@ -4,9 +4,15 @@
 #include "objects.h"
 
 typedef struct {
-	Object         base;
-	int            size;
-	unsigned char *body;
+	int           size,
+	              refs;
+	unsigned char data[];
+} BufferBody;
+
+typedef struct {
+	Object      base;
+	BufferBody *body;
+	int offset, length;
 } BufferObject;
 
 static Object *select(Object *self, Object *key, Heap *heap, Error *err);
@@ -36,18 +42,57 @@ Object *Object_NewBuffer(int size, Heap *heap, Error *error)
 		if(obj == NULL)
 			return NULL;
 
-		obj->size = size;
-		obj->body = Heap_RawMalloc(heap, sizeof(unsigned char) * size, error);
+		obj->offset = 0;
+		obj->length = size;
+		obj->body = Heap_RawMalloc(heap, sizeof(BufferBody) + sizeof(unsigned char) * size, error);
 
 		if(obj->body == NULL)
 			return NULL;
 
-		memset(obj->body, 0, size);
+		obj->body->size = size;
+		obj->body->refs = 1;
+		memset(obj->body->data, 0, size);
 	}
 
 	return (Object*) obj;
 }
 
+Object *Object_SliceBuffer(Object *buffer, int offset, int length, Heap *heap, Error *error)
+{
+	if(buffer->type != &t_buffer)
+		{
+			Error_Report(error, 0, "Not a buffer");
+			return NULL;
+		}
+
+	BufferObject *original = (BufferObject*) buffer;
+	BufferObject *slice = (BufferObject*) Heap_Malloc(heap, &t_buffer, error);
+
+	if(offset < 0 || offset >= original->length)
+		{
+			Error_Report(error, 0, "offset out of range");
+			return NULL;
+		}
+
+	if(length < 0 || length >= original->length)
+		{
+			Error_Report(error, 0, "length out of range");
+			return NULL;
+		}
+
+	if(offset + length > original->length)
+		{
+			Error_Report(error, 0, "slice out of range");
+			return NULL;
+		}
+
+	slice->offset = original->offset + offset;
+	slice->length = length;
+	slice->body = original->body;
+	slice->body->refs += 1;
+	return (Object*) slice;
+}
+
 void *Object_GetBufferAddrAndSize(Object *obj, int *size, Error *error)
 {
 	if(obj->type != &t_buffer)
@@ -59,8 +104,8 @@ void *Object_GetBufferAddrAndSize(Object *obj, int *size, Error *error)
 	BufferObject *buf = (BufferObject*) obj;
 
 	if(size)
-		*size = buf->size;
-	return buf->body;
+		*size = buf->length;
+	return buf->body->data + buf->offset;
 }
 
 static Object *select(Object *self, Object *key, Heap *heap, Error *error)
@@ -82,13 +127,13 @@ static Object *select(Object *self, Object *key, Heap *heap, Error *error)
 
 	BufferObject *buffer = (BufferObject*) self;
 
-	if(idx < 0 || idx >= buffer->size)
+	if(idx < 0 || idx >= buffer->length)
 		{
 			Error_Report(error, 0, "Out of range index");
 			return NULL;
 		}
 
-	unsigned char byte = buffer->body[idx];
+	unsigned char byte = buffer->body->data[buffer->offset + idx];
 
 	return Object_FromInt(byte, heap, error);
 }
@@ -113,7 +158,7 @@ static _Bool insert(Object *self, Object *key, Object *val, Heap *heap, Error *e
 	int idx = Object_ToInt(key, error);
 	assert(error->occurred == 0);
 
-	if(idx < 0 || idx >= buffer->size)
+	if(idx < 0 || idx >= buffer->length)
 		{
 			Error_Report(error, 0, "Out of range index");
 			return NULL;
@@ -124,7 +169,7 @@ static _Bool insert(Object *self, Object *key, Object *val, Heap *heap, Error *e
 	if(error->occurred == 1)
 		return 0;
 
-	buffer->body[idx] = byte;
+	buffer->body->data[buffer->offset + idx] = byte;
 	return 1;
 }
 
@@ -132,7 +177,7 @@ static int count(Object *self)
 {
 	BufferObject *buffer = (BufferObject*) self;
 
-	return buffer->size;
+	return buffer->length;
 }
 
 static void print(Object *self, FILE *fp)
@@ -141,11 +186,11 @@ static void print(Object *self, FILE *fp)
 
 	fprintf(fp, "[");
 
-	for(int i = 0; i < buffer->size; i += 1)
+	for(int i = 0; i < buffer->length; i += 1)
 		{
 			unsigned char byte, low, high;
 
-			byte = buffer->body[i];
+			byte = buffer->body->data[buffer->offset + i];
 			low  = byte & 0xf;
 			high = byte >> 4;
 
@@ -159,7 +204,7 @@ static void print(Object *self, FILE *fp)
 
 			fprintf(fp, "%c%c", c1, c2);
 
-			if(i+1 < buffer->size)
+			if(i+1 < buffer->length)
 				fprintf(fp, ", ");
 		}
 	fprintf(fp, "]");

src/objects/objects.h

@@ -89,6 +89,7 @@ Object*		 Object_NewList(int capacity, Heap *heap, Error *error);
 Object*		 Object_NewNone(Heap *heap, Error *error);
 Object*		 Object_NewBuffer(int size, Heap *heap, Error *error);
 Object*		 Object_NewClosure(Object *parent, Object *new_map, Heap *heap, Error *error);
+Object*		 Object_SliceBuffer(Object *buffer, int offset, int length, Heap *heap, Error *error);
 
 Object*		 Object_FromInt   (long long int val, Heap *heap, Error *error);
 Object*		 Object_FromBool  (_Bool		 val, Heap *heap, Error *error);