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