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/*
* Copyright (c) 2019, The Linux Foundation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of The Linux Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*==============================================================================
FILE: AEEBufBound.c
SERVICES:
AEEBufBound APIs
GENERAL DESCRIPTION:
AEEBufBound provides a "bounded buffer" API that facilitates
measuring strings or character output. It's design accomodates
the implementation of functions that can have the same exact logic
for measuring and outputting char buffer content.
REVISION HISTORY:
Sun Mar 06 11:23:10 2005 Created
==============================================================================*/
#include <limits.h>
#include "AEEBufBound.h"
#include "AEEstd.h"
// Note on bounds-checking logic and saturation:
//
// Simple pointer comparisons are not adequate for bounds checking. pcBuf
// and pcEnd are assumed to be valid pointers in the address space. But
// pcWrite is not ... it is a theoretical value that can exceed pcEnd, and
// may in fact wrap around the end of the address space. In that case the
// test for (pcWrite < pcEnd) will yield TRUE, although pcWrite is outside
// the buffer. Use (pcEnd-pcWrite) > 0 to be accurate.
//
// In order to ensure this works in all cases, we need to avoid integer
// overflows. We do this by restricting pcWrite to the range
// [pcBuf..pcBuf+INT_MAX]. The ensures that pcWrite-pcBuf and pcWrite-pcBuf
// will always be valid integers. It also allows us to ensure that
// BufBound_Wrote() will not return wildly misleading results.
//
// PCSAT
// pcBuf pcEnd pcBuf+MAXINT
// |-------------------| . . . . . . . . . |
// ^ ^
// pcWrite: (a) (b)
//
#define PCSAT(me) ((me)->pcBuf + INT_MAX)
// Advance me->pcWrite, saturating.
//
// On entry:
// *pnLen = number of bytes to be written (non-negative)
// On exit:
// return value = where to write (pointer into the buffer)
// *pnLen = number of bytes to write
//
static char *
BufBound_ValidateWrite(BufBound *me, int *pnLen)
{
int nLen = *pnLen;
char *pcWrite = me->pcWrite;
int nMaxCopy = me->pcEnd - pcWrite; // could be negative!
if ( nMaxCopy < nLen ) {
// Must check PCSAT to validate advance
int nMaxAdvance = PCSAT(me) - pcWrite; // max amount to advance
if (nLen > nMaxAdvance) {
nLen = nMaxAdvance;
}
if (nMaxCopy < 0) {
nMaxCopy = 0;
}
} else {
// Simple case: all fits in the buffer
nMaxCopy = nLen;
}
*pnLen = nMaxCopy;
me->pcWrite = pcWrite + nLen;
return pcWrite;
}
void BufBound_Write(BufBound *me, const char *pc, int nLen)
{
if (nLen > 0) {
char *pcDest = BufBound_ValidateWrite(me, &nLen);
while (--nLen >= 0) {
pcDest[nLen] = pc[nLen];
}
}
}
void BufBound_Putnc(BufBound *me, char c, int nLen)
{
if (nLen > 0) {
char *pcDest = BufBound_ValidateWrite(me, &nLen);
while (--nLen >= 0) {
pcDest[nLen] = c;
}
}
}
void BufBound_Advance(BufBound *me, int nLen)
{
uint32 uOffset = (uint32)((me->pcWrite - me->pcBuf) + nLen);
if (uOffset > INT_MAX) {
uOffset = INT_MAX;
if (nLen < 0) {
uOffset = 0;
}
}
me->pcWrite = me->pcBuf + uOffset;
}
void BufBound_Init(BufBound *me, char *pBuf, int nLen)
{
if (nLen < 0) {
nLen = 0;
}
me->pcWrite = me->pcBuf = pBuf;
me->pcEnd = pBuf + nLen;
}
void BufBound_Putc(BufBound *me, char c)
{
if ( (me->pcEnd - me->pcWrite) > 0) {
*me->pcWrite++ = c;
} else if (me->pcWrite != PCSAT(me)) {
++me->pcWrite;
}
}
void BufBound_ForceNullTerm(BufBound *me)
{
if ( (me->pcEnd - me->pcWrite) > 0) {
*me->pcWrite++ = '\0';
} else {
if (me->pcWrite != PCSAT(me)) {
++me->pcWrite;
}
// ensure null termination if non-empty buffer
if (me->pcEnd != me->pcBuf) {
me->pcEnd[-1] = '\0';
}
}
}
void BufBound_Puts(BufBound *me, const char* cpsz)
{
BufBound_Write(me, cpsz, std_strlen(cpsz));
}
int BufBound_BufSize(BufBound* me)
{
return me->pcEnd - me->pcBuf;
}
int BufBound_Left(BufBound* me)
{
return (me->pcEnd - me->pcWrite);
}
int BufBound_ReallyWrote(BufBound* me)
{
return STD_MIN(me->pcEnd - me->pcBuf, me->pcWrite - me->pcBuf);
}
int BufBound_Wrote(BufBound* me)
{
return (me->pcWrite - me->pcBuf);
}
void BufBound_WriteLE(BufBound *me,
const void *pvSrc, int nSrcSize,
const char *pszFields)
{
if (nSrcSize > 0) {
int nLen = nSrcSize;
char *pcDest = BufBound_ValidateWrite(me, &nLen);
(void)std_CopyLE(pcDest, nLen, pvSrc, nSrcSize, pszFields);
}
}
void BufBound_WriteBE(BufBound *me,
const void *pvSrc, int nSrcSize,
const char *pszFields)
{
if (nSrcSize > 0) {
int nLen = nSrcSize;
char *pcDest = BufBound_ValidateWrite(me, &nLen);
(void)std_CopyBE(pcDest, nLen, pvSrc, nSrcSize, pszFields);
}
}
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