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Added documentation and ASSERT() statements.

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This commit is contained in:
Michael Brown 2005-06-06 12:01:19 +00:00
parent 33dbdda28e
commit df9cbc23cc
1 changed files with 39 additions and 1 deletions
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40
src/core/buffer.c
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@ -66,6 +66,28 @@ void init_buffer ( struct buffer *buffer ) {
DBG ( "BUFFER [%x,%x) initialised\n", buffer->start, buffer->end );
}
/**
* Move to the next block in the free list
*
* @v block The current free block
* @v buffer The buffer
* @ret True Successfully moved to the next free block
* @ret False There are no more free blocks
* @ret block The next free block
* @err None -
*
* Move to the next block in the free block list, filling in @c block
* with the descriptor for this next block. If the next block is the
* tail block, @c block will be filled with the values calculated for
* the tail block, otherwise the descriptor will be read from the free
* block itself.
*
* If there are no more free blocks, next_free_block() returns False
* and leaves @c block with invalid contents.
*
* Set <tt> block->next = buffer->start + buffer->fill </tt> for the
* first call to next_free_block().
*/
static inline int next_free_block ( struct buffer_free_block *block,
struct buffer *buffer ) {
/* Move to next block */
@ -89,6 +111,17 @@ static inline int next_free_block ( struct buffer_free_block *block,
return 1;
}
/**
* Store a free block descriptor
*
* @v block The free block descriptor to store
* @ret None -
* @err None -
*
* Writes a free block descriptor back to a free block. If the block
* is a tail block, only the tail marker will be written, otherwise
* the whole block descriptor will be written.
*/
static inline void store_free_block ( struct buffer_free_block *block ) {
copy_to_phys ( block->start, block,
( block->tail ?
@ -124,7 +157,7 @@ static inline void store_free_block ( struct buffer_free_block *block ) {
* @b NOTE: It is the caller's responsibility to ensure that the
* boundaries between data blocks are more than @c sizeof(struct @c
* buffer_free_block) apart. If this condition is not satisfied, data
* corruption will occur. (See split_free_block() for details.)
* corruption will occur.
*
* In practice this is not a problem. Callers of fill_buffer() will
* be download protocols such as TFTP, and very few protocols have a
@ -175,6 +208,8 @@ int fill_buffer ( struct buffer *buffer, const void *data,
/* Write back 'before' block, if any */
if ( before.start ) {
before.tail = 0;
ASSERT ( ( before.end - before.start ) >=
sizeof ( struct buffer_free_block ) );
store_free_block ( &before );
} else {
buffer->fill = before.next - buffer->start;
@ -182,6 +217,9 @@ int fill_buffer ( struct buffer *buffer, const void *data,
/* Write back 'after' block, if any */
if ( after.start < buffer->end ) {
ASSERT ( after.tail ||
( ( after.end - after.start ) >=
sizeof ( struct buffer_free_block ) ) );
store_free_block ( &after );
}