From: Andre Noll <maan@tuebingen.mpg.de>
Date: Sun, 22 Aug 2021 19:16:48 +0000 (+0200)
Subject: mp4: Kill membuffer API.
X-Git-Tag: v0.7.1~7^2~35
X-Git-Url: http://git.tuebingen.mpg.de/?a=commitdiff_plain;h=eac096021cc916a4fdddf87dc71548e141c208cf;p=paraslash.git

mp4: Kill membuffer API.

Thanks to the previous cleanups, create_ilst() is the last remaining
membuffer user. Since the size of the ilst atom can be computed as the
sum of the tag lengths plus a constant times the number of tag items,
we can allocate a suitably sized buffer up-front instead of relying
on the membuffer framework to allocate and resize buffers as needed.
---

diff --git a/mp4.c b/mp4.c
index 1d8af6cb..1f504fc3 100644
--- a/mp4.c
+++ b/mp4.c
@@ -1083,68 +1083,11 @@ struct mp4_metadata *mp4_get_meta(struct mp4 *f)
 	return &f->meta;
 }
 
-struct membuffer {
-	void *data;
-	unsigned written;
-	unsigned allocated;
-};
-
-static struct membuffer *membuffer_create(void)
-{
-	struct membuffer *buf = para_calloc(sizeof(*buf));
-
-	buf->allocated = 256;
-	buf->data = para_malloc(buf->allocated);
-	return buf;
-}
-
-static void membuffer_write(struct membuffer *buf, const void *ptr,
-		unsigned bytes)
-{
-	unsigned dest_size = buf->written + bytes;
-
-	if (dest_size > buf->allocated) {
-		do {
-			buf->allocated <<= 1;
-		} while (dest_size > buf->allocated);
-		buf->data = para_realloc(buf->data, buf->allocated);
-	}
-
-	if (ptr)
-		memcpy((char *) buf->data + buf->written, ptr, bytes);
-	buf->written += bytes;
-}
-
-static void membuffer_write_atom_name(struct membuffer *buf, const char *data)
-{
-	membuffer_write(buf, data, 4);
-}
-
-static void membuffer_write_int32(struct membuffer *buf, uint32_t data)
+/** Total length of an on-disk metadata tag. */
+#define TAG_LEN(_len) (24 + (_len))
+static void create_ilst(const struct mp4_metadata *meta, uint8_t *out)
 {
-	uint8_t temp[4];
-	write_u32_be(temp, data);
-	membuffer_write(buf, temp, 4);
-}
-
-static unsigned membuffer_get_size(const struct membuffer *buf)
-{
-	return buf->written;
-}
-
-static void *membuffer_detach(struct membuffer *buf)
-{
-	void *ret = para_realloc(buf->data, buf->written);
-	free(buf);
-	return ret;
-}
-
-static void *create_ilst(const struct mp4_metadata *meta, uint32_t *out_size)
-{
-	struct membuffer *buf = membuffer_create();
-	unsigned n;
-
-	for (n = 0; n < meta->count; n++) {
+	for (unsigned n = 0; n < meta->count; n++) {
 		struct mp4_tag *tag = meta->tags + n;
 		unsigned len = strlen(tag->value);
 		const char *atom_name;
@@ -1161,21 +1104,17 @@ static void *create_ilst(const struct mp4_metadata *meta, uint32_t *out_size)
 			atom_name = "\xA9" "cmt";
 		else
 			assert(false);
-		membuffer_write_int32(buf, 8 /* atom header */
-			+ 8 /* data atom header */
-			+ 8 /* flags + reserved */
-			+ len);
-		membuffer_write_atom_name(buf, atom_name);
-		membuffer_write_int32(buf, 8 /* data atom header */
+		write_u32_be(out, TAG_LEN(len));
+		memcpy(out + 4, atom_name, 4);
+		write_u32_be(out + 8, 8 /* data atom header */
 			+ 8 /* flags + reserved */
 			+ len);
-		membuffer_write_atom_name(buf, "data");
-		membuffer_write_int32(buf, 1);	/* flags */
-		membuffer_write_int32(buf, 0);	/* reserved */
-		membuffer_write(buf, tag->value, len);
+		memcpy(out + 12, "data", 4);
+		write_u32_be(out + 16, 1); /* flags */
+		write_u32_be(out + 20, 0); /* reserved */
+		memcpy(out + 24, tag->value, len);
+		out += TAG_LEN(len);
 	}
-	*out_size = membuffer_get_size(buf);
-	return membuffer_detach(buf);
 }
 
 static uint32_t fix_byte_order_32(uint32_t src)
@@ -1188,13 +1127,14 @@ static void *modify_moov(struct mp4 *f, uint32_t *out_size)
 	int ret;
 	uint64_t total_base = f->moov_offset + 8;
 	uint32_t total_size = (uint32_t) (f->moov_size - 8);
-	uint32_t new_ilst_size;
-	void *new_ilst_buffer, *out_buffer;
+	uint32_t new_ilst_size = 0;
+	void *out_buffer;
 	uint8_t *p_out;
 	int32_t size_delta;
 	uint32_t tmp;
 
-	new_ilst_buffer = create_ilst(&f->meta, &new_ilst_size);
+	for (unsigned n = 0; n < f->meta.count; n++)
+		new_ilst_size += TAG_LEN(strlen(f->meta.tags[n].value));
 	size_delta = new_ilst_size - (f->ilst_size - 8);
 	*out_size = total_size + size_delta;
 	out_buffer = para_malloc(*out_size);
@@ -1239,14 +1179,13 @@ static void *modify_moov(struct mp4 *f, uint32_t *out_size)
 	if (ret <= 0)
 		return NULL;
 	p_out += 4;
-	memcpy(p_out, new_ilst_buffer, new_ilst_size);
+	create_ilst(&f->meta, p_out);
 	p_out += new_ilst_size;
 	set_position(f, f->ilst_offset + f->ilst_size);
 	ret = read_data(f, p_out, total_size - (f->ilst_offset - total_base)
 		- f->ilst_size);
 	if (ret <= 0)
 		return NULL;
-	free(new_ilst_buffer);
 	return out_buffer;
 }