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Return -1 to indicate buffer overflow. Allow buffer fill level to be read

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easily from struct buffer.
This commit is contained in:
Michael Brown 2005-05-09 14:26:10 +00:00
parent a89651f3bb
commit bab2924e89
2 changed files with 32 additions and 23 deletions
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32
src/core/buffer.c
View File

@ -35,7 +35,7 @@
void init_buffer ( struct buffer *buffer, physaddr_t start, size_t len ) {
buffer->start = start;
buffer->end = start + len;
buffer->first_free = start;
buffer->fill = 0;
if ( len ) {
char tail = 1;
@ -59,7 +59,7 @@ static void split_free_block ( struct buffer_free_block *desc,
if ( split >= desc->end )
return;
DBG ( "BUFFER splitting [%x,%x) into [%x,%x) and [%x,%x)\n",
DBG ( "BUFFER splitting [%x,%x) -> [%x,%x) [%x,%x)\n",
block, desc->end, block, split, split, desc->end );
/* Create descriptor for new free block */
@ -83,11 +83,11 @@ static inline void unfree_block ( struct buffer *buffer,
physaddr_t prev_block ) {
struct buffer_free_block prev_desc;
/* If this is the first block, just update first_free */
/* If this is the first block, just update buffer->fill */
if ( ! prev_block ) {
DBG ( "BUFFER marking [%x,%x) as used\n",
buffer->first_free, desc->end );
buffer->first_free = desc->next_free;
buffer->start + buffer->fill, desc->end );
buffer->fill = desc->next_free - buffer->start;
return;
}
@ -110,13 +110,10 @@ static inline void unfree_block ( struct buffer *buffer,
* apart. If this condition is not satisfied, data corruption will
* occur.
*
* Returns the offset to the first gap in the buffer. (When the
* buffer is full, returns the offset to the byte past the end of the
* buffer.)
*
* Returns 1 for success, 0 for failure (e.g. buffer too small).
*/
off_t fill_buffer ( struct buffer *buffer, void *data,
off_t offset, size_t len ) {
int fill_buffer ( struct buffer *buffer, void *data,
off_t offset, size_t len ) {
struct buffer_free_block desc;
physaddr_t block, prev_block;
physaddr_t data_start, data_end;
@ -127,9 +124,16 @@ off_t fill_buffer ( struct buffer *buffer, void *data,
DBG ( "BUFFER [%x,%x) writing portion [%x,%x)\n",
buffer->start, buffer->end, data_start, data_end );
/* Check buffer bounds */
if ( data_end > buffer->end ) {
DBG ( "BUFFER [%x,%x) too small for data!\n",
buffer->start, buffer->end );
return 0;
}
/* Iterate through the buffer's free blocks */
prev_block = 0;
block = buffer->first_free;
block = buffer->start + buffer->fill;
while ( block < buffer->end ) {
/* Read block descriptor */
desc.next_free = buffer->end;
@ -160,7 +164,7 @@ off_t fill_buffer ( struct buffer *buffer, void *data,
}
DBG ( "BUFFER [%x,%x) full up to %x\n",
buffer->start, buffer->end, buffer->first_free );
buffer->start, buffer->end, buffer->start + buffer->fill );
return ( buffer->first_free - buffer->start );
return 1;
}

23
src/include/buffer.h
View File

@ -3,6 +3,18 @@
#include "stdint.h"
/*
* "start" and "end" denote the real boundaries of the buffer. "fill"
* denotes the offset to the first free block in the buffer. (If the
* buffer is full, "fill" will equal ( end - start ) ).
*
*/
struct buffer {
physaddr_t start;
physaddr_t end;
off_t fill;
};
/*
* Free blocks in the buffer start with a "tail byte". If non-zero,
* this byte indicates that the free block is the tail of the buffer,
@ -15,24 +27,17 @@
* smaller than a struct buffer_free_block.
*
*/
struct buffer_free_block {
char tail;
physaddr_t next_free;
physaddr_t end;
} __attribute__ (( packed ));
struct buffer {
physaddr_t start;
physaddr_t end;
physaddr_t first_free;
};
/* Functions in buffer.c */
extern void init_buffer ( struct buffer *buffer, physaddr_t start,
size_t len );
extern off_t fill_buffer ( struct buffer *buffer, void *data,
off_t offset, size_t len );
extern int fill_buffer ( struct buffer *buffer, void *data,
off_t offset, size_t len );
#endif /* BUFFER_H */