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Diffstat (limited to 'lib/libpcap/libpcap/missing/asprintf.c')
-rw-r--r-- | lib/libpcap/libpcap/missing/asprintf.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/lib/libpcap/libpcap/missing/asprintf.c b/lib/libpcap/libpcap/missing/asprintf.c new file mode 100644 index 0000000..3aa55ed --- /dev/null +++ b/lib/libpcap/libpcap/missing/asprintf.c @@ -0,0 +1,101 @@ +#include <stdio.h> +#include <stdlib.h> +#include <stdarg.h> + +#include "portability.h" + +/* + * vasprintf() and asprintf() for platforms with a C99-compliant + * snprintf() - so that, if you format into a 1-byte buffer, it + * will return how many characters it would have produced had + * it been given an infinite-sized buffer. + */ +int +pcap_vasprintf(char **strp, const char *format, va_list args) +{ + char buf; + int len; + size_t str_size; + char *str; + int ret; + + /* + * XXX - the C99 standard says, in section 7.19.6.5 "Thes + * nprintf function": + * + * The snprintf function is equivalent to fprintf, except that + * the output is written into an array (specified by argument s) + * rather than to a stream. If n is zero, nothing is written, + * and s may be a null pointer. Otherwise, output characters + * beyond the n-1st are discarded rather than being written + * to the array, and a null character is written at the end + * of the characters actually written into the array. + * + * ... + * + * The snprintf function returns the number of characters that + * would have been written had n been sufficiently large, not + * counting the terminating null character, or a negative value + * if an encoding error occurred. Thus, the null-terminated + * output has been completely written if and only if the returned + * value is nonnegative and less than n. + * + * That doesn't make it entirely clear whether, if a null buffer + * pointer and a zero count are passed, it will return the number + * of characters that would have been written had a buffer been + * passed. + * + * And, even if C99 *does*, in fact, say it has to work, it + * doesn't work in Solaris 8, for example - it returns -1 for + * NULL/0, but returns the correct character count for a 1-byte + * buffer. + * + * So we pass a one-character pointer in order to find out how + * many characters this format and those arguments will need + * without actually generating any more of those characters + * than we need. + * + * (The fact that it might happen to work with GNU libc or with + * various BSD libcs is completely uninteresting, as those tend + * to have asprintf() already and thus don't even *need* this + * code; this is for use in those UN*Xes that *don't* have + * asprintf().) + */ + len = vsnprintf(&buf, sizeof buf, format, args); + if (len == -1) { + *strp = NULL; + return (-1); + } + str_size = len + 1; + str = malloc(str_size); + if (str == NULL) { + *strp = NULL; + return (-1); + } + ret = vsnprintf(str, str_size, format, args); + if (ret == -1) { + free(str); + *strp = NULL; + return (-1); + } + *strp = str; + /* + * vsnprintf() shouldn't truncate the string, as we have + * allocated a buffer large enough to hold the string, so its + * return value should be the number of characters written. + */ + return (ret); +} + +int +pcap_asprintf(char **strp, const char *format, ...) +{ + va_list args; + int ret; + + va_start(args, format); + ret = pcap_vasprintf(strp, format, args); + va_end(args); + return (ret); +} + |