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Extend buflib to support shifting space out off the buffer for other use, and returning space to the buffer.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@20952 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andrew Mahone 2009-05-16 00:45:08 +00:00
parent d59bff092d
commit c909878f94
2 changed files with 53 additions and 0 deletions
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48
apps/plugins/lib/buflib.c
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@ -61,6 +61,7 @@ buflib_init(struct buflib_context *ctx, void *buf, size_t size)
ctx->last_handle = bd_buf + size;
ctx->first_free_handle = bd_buf + size - 1;
ctx->first_free_block = bd_buf;
ctx->buf_start = bd_buf;
/* A marker is needed for the end of allocated data, to make sure that it
* does not collide with the handle table, and to detect end-of-buffer.
*/
@ -167,6 +168,53 @@ buflib_compact(struct buflib_context *ctx)
return ret || shift;
}
/* Shift buffered items by size units, and update handle pointers. The shift
* value must be determined to be safe *before* calling.
*/
static void
buflib_buffer_shift(struct buflib_context *ctx, int shift)
{
rb->memmove(ctx->buf_start + shift, ctx->buf_start,
(ctx->alloc_end - ctx->buf_start) * sizeof(union buflib_data));
union buflib_data *ptr;
for (ptr = ctx->last_handle; ptr < ctx->handle_table; ptr++)
if (ptr->ptr)
ptr->ptr += shift;
ctx->first_free_block += shift;
ctx->buf_start += shift;
ctx->alloc_end += shift;
}
/* Shift buffered items up by size bytes, or as many as possible if size == 0.
* Set size to the number of bytes freed.
*/
void*
buflib_buffer_out(struct buflib_context *ctx, size_t *size)
{
if (!ctx->compact)
buflib_compact(ctx);
size_t avail = ctx->last_handle - ctx->alloc_end;
size_t avail_b = avail * sizeof(union buflib_data);
if (*size && *size < avail_b)
{
avail = (*size + sizeof(union buflib_data) - 1)
/ sizeof(union buflib_data);
avail_b = avail * sizeof(union buflib_data);
}
*size = avail_b;
void *ret = ctx->buf_start;
buflib_buffer_shift(ctx, avail);
return ret;
}
/* Shift buffered items down by size bytes */
void
buflib_buffer_in(struct buflib_context *ctx, int size)
{
size /= sizeof(union buflib_data);
buflib_buffer_shift(ctx, -size);
}
/* Allocate a buffer of size bytes, returning a handle for it */
int
buflib_alloc(struct buflib_context *ctx, size_t size)