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/*
* include/common/buf.h
* Simple buffer handling.
*
* Copyright (C) 2000-2018 Willy Tarreau - w@1wt.eu
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef _COMMON_BUF_H
#define _COMMON_BUF_H
#include <stdint.h>
/* Structure defining a buffer's head */
struct buffer {
char *p; /* buffer's start pointer, separates in and out data */
size_t size; /* buffer size in bytes */
size_t i; /* number of input bytes pending for analysis in the buffer */
size_t o; /* number of out bytes the sender can consume from this buffer */
char data[0]; /* <size> bytes of stored data */
};
/***************************************************************************/
/* Functions used to compute offsets and pointers. Most of them exist in */
/* both wrapping-safe and unchecked ("__" prefix) variants. Some returning */
/* a pointer are also provided with an "_ofs" suffix when they return an */
/* offset relative to the storage area. */
/***************************************************************************/
/* b_orig() : returns the pointer to the origin of the storage, which is the
* location of byte at offset zero. This is mostly used by functions which
* handle the wrapping by themselves.
*/
static inline char *b_orig(const struct buffer *b)
{
return (char *)b->data;
}
/* b_size() : returns the size of the buffer. */
static inline size_t b_size(const struct buffer *b)
{
return b->size;
}
/* b_wrap() : returns the pointer to the wrapping position of the buffer area,
* which is by definition the first byte not part of the buffer.
*/
static inline char *b_wrap(const struct buffer *b)
{
return (char *)b->data + b->size;
}
/* b_data() : returns the number of bytes present in the buffer. */
static inline size_t b_data(const struct buffer *b)
{
return b->i + b->o;
}
/* b_room() : returns the amount of room left in the buffer */
static inline size_t b_room(const struct buffer *b)
{
return b->size - b_data(b);
}
/* b_full() : returns true if the buffer is full. */
static inline size_t b_full(const struct buffer *b)
{
return !b_room(b);
}
/* b_stop() : returns the pointer to the byte following the end of the buffer,
* which may be out of the buffer if the buffer ends on the last byte of the
* area.
*/
static inline size_t __b_stop_ofs(const struct buffer *b)
{
return b->p - b->data + b->i;
}
static inline const char *__b_stop(const struct buffer *b)
{
return b->p + b->i;
}
static inline size_t b_stop_ofs(const struct buffer *b)
{
size_t stop = __b_stop_ofs(b);
if (stop > b->size)
stop -= b->size;
return stop;
}
static inline const char *b_stop(const struct buffer *b)
{
return b->data + b_stop_ofs(b);
}
/* b_peek() : returns a pointer to the data at position <ofs> relative to the
* head of the buffer. Will typically point to input data if called with the
* amount of output data. The wrapped versions will only support wrapping once
* before the beginning or after the end.
*/
static inline size_t __b_peek_ofs(const struct buffer *b, size_t ofs)
{
return b->p - b->data + ofs - b->o;
}
static inline char *__b_peek(const struct buffer *b, size_t ofs)
{
return b->p - b->o + ofs;
}
static inline size_t b_peek_ofs(const struct buffer *b, size_t ofs)
{
size_t ret = __b_peek_ofs(b, ofs);
if (ret >= b->size) {
/* wraps either up or down */
if ((ssize_t)ret < 0)
ret += b->size;
else
ret -= b->size;
}
return ret;
}
static inline char *b_peek(const struct buffer *b, size_t ofs)
{
return (char *)b->data + b_peek_ofs(b, ofs);
}
/* b_head() : returns the pointer to the buffer's head, which is the location
* of the next byte to be dequeued. Note that for buffers of size zero, the
* returned pointer may be outside of the buffer or even invalid.
*/
static inline size_t __b_head_ofs(const struct buffer *b)
{
return __b_peek_ofs(b, 0);
}
static inline char *__b_head(const struct buffer *b)
{
return __b_peek(b, 0);
}
static inline size_t b_head_ofs(const struct buffer *b)
{
return b_peek_ofs(b, 0);
}
static inline char *b_head(const struct buffer *b)
{
return b_peek(b, 0);
}
/* b_tail() : returns the pointer to the tail of the buffer, which is the
* location of the first byte where it is possible to enqueue new data. Note
* that for buffers of size zero, the returned pointer may be outside of the
* buffer or even invalid.
*/
static inline size_t __b_tail_ofs(const struct buffer *b)
{
return __b_peek_ofs(b, b_data(b));
}
static inline char *__b_tail(const struct buffer *b)
{
return __b_peek(b, b_data(b));
}
static inline size_t b_tail_ofs(const struct buffer *b)
{
return b_peek_ofs(b, b_data(b));
}
static inline char *b_tail(const struct buffer *b)
{
return b_peek(b, b_data(b));
}
/* b_next() : for an absolute pointer <p> or a relative offset <o> pointing to
* a valid location within buffer <b>, returns either the absolute pointer or
* the relative offset pointing to the next byte, which usually is at (p + 1)
* unless p reaches the wrapping point and wrapping is needed.
*/
static inline size_t b_next_ofs(const struct buffer *b, size_t o)
{
o++;
if (o == b->size)
o = 0;
return o;
}
static inline char *b_next(const struct buffer *b, const char *p)
{
p++;
if (p == b_wrap(b))
p = b_orig(b);
return (char *)p;
}
/* b_dist() : returns the distance between two pointers, taking into account
* the ability to wrap around the buffer's end. The operation is not defined if
* either of the pointers does not belong to the buffer or if their distance is
* greater than the buffer's size.
*/
static inline size_t b_dist(const struct buffer *b, const char *from, const char *to)
{
ssize_t dist = to - from;
dist += dist < 0 ? b_size(b) : 0;
return dist;
}
/* b_almost_full() : returns 1 if the buffer uses at least 3/4 of its capacity,
* otherwise zero. Buffers of size zero are considered full.
*/
static inline int b_almost_full(const struct buffer *b)
{
return b_data(b) >= b_size(b) * 3 / 4;
}
/* b_space_wraps() : returns non-zero only if the buffer's free space wraps :
* [ |oooo| ] => yes
* [ |iiii| ] => yes
* [ |oooo|iiii| ] => yes
* [oooo| ] => no
* [ |oooo] => no
* [iiii| ] => no
* [ |iiii] => no
* [oooo|iiii| ] => no
* [ |oooo|iiii] => no
* [iiii| |oooo] => no
* [oo|iiii| |oo] => no
* [iiii| |oo|ii] => no
* [oooooooooo|iiiiiiiiiii] => no
* [iiiiiiiiiiiii|oooooooo] => no
*
* So the only case where the buffer does not wrap is when there's data either
* at the beginning or at the end of the buffer. Thus we have this :
* - if (head <= 0) ==> doesn't wrap
* - if (tail >= size) ==> doesn't wrap
* - otherwise wraps
*/
static inline int b_space_wraps(const struct buffer *b)
{
if ((ssize_t)__b_head_ofs(b) <= 0)
return 0;
if (__b_tail_ofs(b) >= b_size(b))
return 0;
return 1;
}
/* b_contig_data() : returns the amount of data that can contiguously be read
* at once starting from a relative offset <start> (which allows to easily
* pre-compute blocks for memcpy). The start point will typically contain the
* amount of past data already returned by a previous call to this function.
*/
static inline size_t b_contig_data(const struct buffer *b, size_t start)
{
size_t data = b_wrap(b) - b_peek(b, start);
size_t limit = b_data(b) - start;
if (data > limit)
data = limit;
return data;
}
/* b_contig_space() : returns the amount of bytes that can be appended to the
* buffer at once.
*/
static inline size_t b_contig_space(const struct buffer *b)
{
const char *left, *right;
right = b_head(b);
left = right + b_data(b);
if (left >= b_wrap(b))
left -= b_size(b);
else
right = b_wrap(b);
return right - left;
}
/* b_getblk() : gets one full block of data at once from a buffer, starting
* from offset <offset> after the buffer's head, and limited to no more than
* <len> bytes. The caller is responsible for ensuring that neither <offset>
* nor <offset>+<len> exceed the total number of bytes available in the buffer.
* Return values :
* >0 : number of bytes read, equal to requested size.
* =0 : not enough data available. <blk> is left undefined.
* The buffer is left unaffected.
*/
static inline size_t b_getblk(const struct buffer *buf, char *blk, size_t len, size_t offset)
{
size_t firstblock;
if (len + offset > b_data(buf))
return 0;
firstblock = b_wrap(buf) - b_head(buf);
if (firstblock > offset) {
if (firstblock >= len + offset) {
memcpy(blk, b_head(buf) + offset, len);
return len;
}
memcpy(blk, b_head(buf) + offset, firstblock - offset);
memcpy(blk + firstblock - offset, b_orig(buf), len - firstblock + offset);
return len;
}
memcpy(blk, b_orig(buf) + offset - firstblock, len);
return len;
}
/* b_getblk_nc() : gets one or two blocks of data at once from a buffer,
* starting from offset <ofs> after the beginning of its output, and limited to
* no more than <max> bytes. The caller is responsible for ensuring that
* neither <ofs> nor <ofs>+<max> exceed the total number of bytes available in
* the buffer. Return values :
* >0 : number of blocks filled (1 or 2). blk1 is always filled before blk2.
* =0 : not enough data available. <blk*> are left undefined.
* The buffer is left unaffected. Unused buffers are left in an undefined state.
*/
static inline size_t b_getblk_nc(struct buffer *buf, char **blk1, int *len1, char **blk2, int *len2, size_t ofs, size_t max)
{
size_t l1;
if (!max)
return 0;
*blk1 = b_peek(buf, ofs);
l1 = b_wrap(buf) - *blk1;
if (l1 < max) {
*len1 = l1;
*len2 = max - l1;
*blk2 = buf->data;
return 2;
}
*len1 = max;
return 1;
}
/*********************************************/
/* Functions used to modify the buffer state */
/*********************************************/
/* b_reset() : resets a buffer. The size is not touched. */
static inline void b_reset(struct buffer *b)
{
b->o = 0;
b->i = 0;
b->p = b_orig(b);
}
/* b_sub() : decreases the buffer length by <count> */
static inline void b_sub(struct buffer *b, size_t count)
{
b->i -= count;
}
/* b_add() : increase the buffer length by <count> */
static inline void b_add(struct buffer *b, size_t count)
{
b->i += count;
}
/* bo_add() : increase the buffer output and length by <count>
* (LEGACY API)
*/
static inline void bo_add(struct buffer *b, size_t count)
{
b->o += count;
}
/* b_set_data() : sets the buffer's length */
static inline void b_set_data(struct buffer *b, size_t len)
{
if (len >= b->o)
b->i = len - b->o;
else {
b->o = len;
b->i = 0;
}
}
/* b_del() : skips <del> bytes in a buffer <b>. Covers both the output and the
* input parts so it's up to the caller to know where it plays and that <del>
* is always smaller than the amount of data in the buffer.
*/
static inline void b_del(struct buffer *b, size_t del)
{
if (del <= b->o) {
b->o -= del;
del = 0;
}
if (del) {
b->p = b_peek(b, del);
b->i -= del;
del = 0;
}
}
/* b_realign_if_empty() : realigns a buffer if it's empty */
static inline void b_realign_if_empty(struct buffer *b)
{
if (!b_data(b))
b->p = b->data;
}
/* b_slow_realign() : this function realigns a possibly wrapping buffer so that
* the part remaining to be parsed is contiguous and starts at the beginning of
* the buffer and the already parsed output part ends at the end of the buffer.
* This provides the best conditions since it allows the largest inputs to be
* processed at once and ensures that once the output data leaves, the whole
* buffer is available at once. The number of output bytes supposedly present
* at the beginning of the buffer and which need to be moved to the end must be
* passed in <output>. A temporary swap area at least as large as b->size must
* be provided in <swap>. It's up to the caller to ensure <output> is no larger
* than the difference between the whole buffer's length and its input.
*/
static inline void b_slow_realign(struct buffer *b, char *swap, size_t output)
{
size_t block1 = output;
size_t block2 = 0;
/* process output data in two steps to cover wrapping */
if (block1 > b_size(b) - b_head_ofs(b)) {
block2 = b_size(b) - b_head_ofs(b);
block1 -= block2;
}
memcpy(swap + b_size(b) - output, b_head(b), block1);
memcpy(swap + b_size(b) - block2, b_orig(b), block2);
/* process input data in two steps to cover wrapping */
block1 = b_data(b) - output;
block2 = 0;
if (block1 > b_tail_ofs(b)) {
block2 = b_tail_ofs(b);
block1 = block1 - block2;
}
memcpy(swap, b_peek(b, output), block1);
memcpy(swap + block1, b_orig(b), block2);
/* reinject changes into the buffer */
memcpy(b_orig(b), swap, b_data(b) - output);
memcpy(b_wrap(b) - output, swap + b_size(b) - output, output);
b->p = b->data;
}
#endif /* _COMMON_BUF_H */
/*
* Local variables:
* c-indent-level: 8
* c-basic-offset: 8
* End:
*/