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util: Add xa{v}sprintf_append functions

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Add variadic and va_list functions, xa{v}sprintf, which appends a
formatted string to an existing string and re-allocate the string buffer
if necessary. xasprintf becomes just a special case of xasprintf_append
with a NULL starting string.

Rather than looping to get a big enough buffer, simply the implementation
by assuming we have a C99 compliant vsnprintf implementation to return the
necessary size. A side effect is glibc 2.0 support is dropped which seems
unnecessary.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Rob Herring 2018-11-24 14:47:54 -06:00 committed by David Gibson
parent 82a52ce457
commit a1eff70c02
2 changed files with 41 additions and 21 deletions
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60
util.c
View file

@ -46,36 +46,54 @@ char *xstrdup(const char *s)
return d;
}
/* based in part from (3) vsnprintf */
int xasprintf(char **strp, const char *fmt, ...)
int xavsprintf_append(char **strp, const char *fmt, va_list ap)
{
int n, size = 128; /* start with 128 bytes */
int n, size = 0; /* start with 128 bytes */
char *p;
va_list ap;
va_list ap_copy;
/* initial pointer is NULL making the fist realloc to be malloc */
p = NULL;
while (1) {
p = xrealloc(p, size);
p = *strp;
if (p)
size = strlen(p);
/* Try to print in the allocated space. */
va_start(ap, fmt);
n = vsnprintf(p, size, fmt, ap);
va_end(ap);
va_copy(ap_copy, ap);
n = vsnprintf(NULL, 0, fmt, ap_copy) + 1;
va_end(ap_copy);
p = xrealloc(p, size + n);
n = vsnprintf(p + size, n, fmt, ap);
/* If that worked, return the string. */
if (n > -1 && n < size)
break;
/* Else try again with more space. */
if (n > -1) /* glibc 2.1 */
size = n + 1; /* precisely what is needed */
else /* glibc 2.0 */
size *= 2; /* twice the old size */
}
*strp = p;
return strlen(p);
}
int xasprintf_append(char **strp, const char *fmt, ...)
{
int n;
va_list ap;
va_start(ap, fmt);
n = xavsprintf_append(strp, fmt, ap);
va_end(ap);
return n;
}
int xasprintf(char **strp, const char *fmt, ...)
{
int n;
va_list ap;
*strp = NULL;
va_start(ap, fmt);
n = xavsprintf_append(strp, fmt, ap);
va_end(ap);
return n;
}
char *join_path(const char *path, const char *name)
{
int lenp = strlen(path);

2
util.h
View file

@ -72,6 +72,8 @@ static inline void *xrealloc(void *p, size_t len)
extern char *xstrdup(const char *s);
extern int PRINTF(2, 3) xasprintf(char **strp, const char *fmt, ...);
extern int PRINTF(2, 3) xasprintf_append(char **strp, const char *fmt, ...);
extern int xavsprintf_append(char **strp, const char *fmt, va_list ap);
extern char *join_path(const char *path, const char *name);
/**