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Extend path_append_ex to truncate compname, remove some strmemdupa

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remove some duplicated strings previously allocd off the stack

just removing string duplications that are easily handled with truncation
now available with path_append_ex()

this also has an advantage of less stack used in worst case scenarios

Change-Id: I3a43e33ef8a8c36599e4c6c036a0ccdd8ed0c883
This commit is contained in:
William Wilgus 2023-11-11 00:01:34 -05:00 • committed by William Wilgus
parent a7d0ff2000
commit dbe20d453d
6 changed files with 122 additions and 56 deletions
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69
firmware/common/pathfuncs.c
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@ -447,10 +447,22 @@ void path_remove_dot_segments (char *dstpath, const char *path)
*dstp = 0;
}
/* helper function copy n chars of a string to a dst buffer of dst_sz
* returns the length of the string it created or attempted to create
*/
static inline size_t copynchars(char *dst, size_t dst_sz, const char *src, size_t src_max)
{
int cpychrs = -1;
if (src_max < -1u) /* we could be dealing with unterminated strings */
cpychrs = src_max;
/* testing shows this to be on par with using discreet functions and safer ;) */
int ret = snprintf(dst, dst_sz, "%.*s", cpychrs, src);
if (ret >= 0)
return ret;
return 0; /* Error */
}
/* Appends one path to another, adding separators between components if needed.
* basepath_max can be used to truncate the basepath if desired
* NOTE: basepath is truncated after copying to the buffer so there must be enough
* free space for the entirety of the basepath even if the resulting string would fit
*
* Return value and behavior is otherwise as strlcpy so that truncation may be
* detected.
@ -458,45 +470,52 @@ void path_remove_dot_segments (char *dstpath, const char *path)
* For basepath and component:
* PA_SEP_HARD adds a separator even if the base path is empty
* PA_SEP_SOFT adds a separator only if the base path is not empty
*
* basepath_max can be used to truncate the basepath if desired
* component_max can be used to truncate the component if desired
*
* (Supply -1u to disable truncation)
*/
size_t path_append_ex(char *buf, const char *basepath, size_t basepath_max,
const char *component, size_t bufsize)
const char *component, size_t component_max, size_t bufsize)
{
size_t len;
bool check_base = (basepath_max == 0);
bool separate = false;
const char *base = basepath && basepath[0] ? basepath : buf;
const char *base = basepath && !check_base && basepath[0] ? basepath : buf;
if (!base)
return bufsize; /* won't work to get lengths from buf */
if (!buf)
{
static char fbuf; /* fake buffer to elide later null checks */
buf = &fbuf;
bufsize = 0;
}
if (!component)
{
check_base = true;
component = "";
}
if (path_is_absolute(component))
{
/* 'component' is absolute; replace all */
basepath = component;
basepath_max = component_max;
component = "";
basepath_max = -1u;
}
/* if basepath is not null or empty, buffer contents are replaced,
otherwise buf contains the base path */
if (base == buf)
len = strlen(buf);
else
{
len = strlcpy(buf, basepath, bufsize);
if (basepath_max < len)
{
len = basepath_max;
buf[basepath_max] = '\0';
}
}
len = copynchars(buf, bufsize, basepath, basepath_max);
if (!basepath || !component || basepath_max == 0)
if (!basepath || basepath_max == 0 || check_base)
separate = !len || base[len-1] != PATH_SEPCH;
else if (component[0])
else if (component[0] && component_max > 0)
separate = len && base[len-1] != PATH_SEPCH;
/* caller might lie about size of buf yet use buf as the base */
@ -509,14 +528,22 @@ size_t path_append_ex(char *buf, const char *basepath, size_t basepath_max,
if (separate && (len++, bufsize > 0) && --bufsize > 0)
*buf++ = PATH_SEPCH;
return len + strlcpy(buf, component ?: "", bufsize);
return len + copynchars(buf, bufsize, component, component_max);
}
/* Appends one path to another, adding separators between components if needed.
*
* Return value and behavior is otherwise as strlcpy so that truncation may be
* detected.
*
* For basepath and component:
* PA_SEP_HARD adds a separator even if the base path is empty
* PA_SEP_SOFT adds a separator only if the base path is not empty
*/
size_t path_append(char *buf, const char *basepath,
const char *component, size_t bufsize)
{
return path_append_ex(buf, basepath, -1u, component, bufsize);
return path_append_ex(buf, basepath, -1u, component, -1u, bufsize);
}
/* Returns the location and length of the next path component, consuming the
* input in the process.