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/*
* Determine whether a string looks like valid base64-encoded data.
*/
#include "misc.h"
static inline bool valid_char_main(char c)
{
return ((c >= 'A' && c <= 'Z') ||
(c >= 'a' && c <= 'z') ||
(c >= '0' && c <= '9') ||
c == '+' || c == '/');
}
bool base64_valid(ptrlen data)
{
size_t blocklen = 0, nequals = 0;
for (size_t i = 0; i < data.len; i++) {
char c = ((const char *)data.ptr)[i];
if (c == '\n' || c == '\r')
continue;
if (valid_char_main(c)) {
if (nequals) /* can't go back to data after = */
return false;
blocklen++;
if (blocklen == 4)
blocklen = 0;
continue;
}
if (c == '=') {
if (blocklen == 0 && nequals) /* started a fresh block */
return false;
nequals++;
blocklen++;
if (blocklen == 4) {
if (nequals > 2)
return false; /* nonsensical final block */
blocklen = 0;
}
continue;
}
return false; /* bad character */
}
if (blocklen == 0 || blocklen == 2 || blocklen == 3)
return true; /* permit eliding the trailing = */
return false;
}
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