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 1d8af6cb20853c33a4aff5d151eb143951bd5a90..1f504fc30ee06231cd442cb4bceafe32497792b6 100644 (file)
--- 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;
 }