When one detects a non-printable char, output an escape sequence or hexadecimal value
#include <ctype.h>
#include <string.h>
#include <stdio.h>
int printf_ByteArray(const unsigned char *data, size_t len) {
size_t i;
int result = 0;
for (i = 0; i < len; i++) {
int y;
int ch = data[i];
static const char escapec[] = "\a\b\t\n\v\f\n\'\"\?\\";
char *p = strchr(escapec, ch);
if (p && ch) {
static const char escapev[] = "abtnvfn\'\"\?\\";
y = printf("\\%c", escapev[p - escapec]);
} else if (isprint(ch)) {
y = printf("%c", ch);
} else {
// If at end of array, assume _next_ potential character is a '0'.
int nch = i >= (len - 1) ? '0' : data[i + 1];
if (ch < 8 && (nch < '0' || nch > '7')) {
y = printf("\\%o", ch);
} else if (!isxdigit(nch)) {
y = printf("\\x%X", ch);
} else {
y = printf("\\o%03o", ch);
}
}
if (y == EOF)
return EOF;
result += y;
}
return result;
}
If data
contained one of each byte, sample follows:
\0...\6\a\b\t\n\v\f\xD\xE\xF\x10...\x1F !\"#$%&\'()*+,-./0123456789:;<=>\?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F...\xFE\o377
The selection of escape sequences will vary with code goals. The set above attempts to conform to something a C parser would accept.
Note: With the last else
, always outputting a 3-digit octal sequence has scanning advantages, but folks are more accustomed to hexadecimal than octal.
Adjusted to conditionally print in hex depending on the following character.