buffer: add buffer_insert to insert data at an arbitrary position

Use it to implement buffer_{pre,ap}pend.

2 files changed, 23 insertions, 10 deletions

diff --git a/buffer.c b/buffer.c
index 3cdf65a..6a16a7b 100644
--- a/buffer.c
+++ b/buffer.c
@@ -48,15 +48,29 @@ bool buffer_put0(Buffer *buf, const char *data) {
 	return buffer_put(buf, data, strlen(data)+1);
 }
 
-bool buffer_append(Buffer *buf, const void *data, size_t len) {
-	size_t rem = buf->size - buf->len;
-	if (len > rem && !buffer_grow(buf, buf->size + len - rem))
+bool buffer_insert(Buffer *buf, size_t pos, const void *data, size_t len) {
+	if (pos > buf->len)
+		return false;
+	if (!buffer_grow(buf, buf->len + len))
 		return false;
-	memcpy(buf->data + buf->len, data, len);
+	memmove(buf->data + pos + len, buf->data + pos, buf->len - pos);
+	memcpy(buf->data + pos, data, len);
 	buf->len += len;
 	return true;
 }
 
+bool buffer_insert0(Buffer *buf, size_t pos, const char *data) {
+	if (pos == 0)
+		return buffer_prepend0(buf, data);
+	if (pos == buf->len)
+		return buffer_append0(buf, data);
+	return buffer_insert(buf, pos, data, strlen(data));
+}
+
+bool buffer_append(Buffer *buf, const void *data, size_t len) {
+	return buffer_insert(buf, buf->len, data, len);
+}
+
 bool buffer_append0(Buffer *buf, const char *data) {
 	if (buf->len > 0 && buf->data[buf->len-1] == '\0')
 		buf->len--;
@@ -64,12 +78,7 @@ bool buffer_append0(Buffer *buf, const char *data) {
 }
 
 bool buffer_prepend(Buffer *buf, const void *data, size_t len) {
-	if (!buffer_grow(buf, buf->len + len))
-		return false;
-	memmove(buf->data + len, buf->data, buf->len);
-	memcpy(buf->data, data, len);
-	buf->len += len;
-	return true;
+	return buffer_insert(buf, 0, data, len);
 }
 
 bool buffer_prepend0(Buffer *buf, const char *data) {
diff --git a/buffer.h b/buffer.h
index 85679c8..4c5ae33 100644
--- a/buffer.h
+++ b/buffer.h
@@ -23,6 +23,10 @@ void buffer_truncate(Buffer*);
 bool buffer_put(Buffer*, const void *data, size_t len);
 /* same but with NUL-terminated data */
 bool buffer_put0(Buffer*, const char *data);
+/* insert arbitrary data of length len at pos (in [0, buf->len]) */
+bool buffer_insert(Buffer*, size_t pos, const void *data, size_t len);
+/* insert NUL-terminate data at pos (in [0, buf->len]) */
+bool buffer_insert0(Buffer*, size_t pos, const char *data);
 /* append futher content to the end of the buffer data */
 bool buffer_append(Buffer*, const void *data, size_t len);
 /* append NUl-terminated data */