OVMS3/OVMS.V3/components/duktape/extras/minimal-printf/duk_minimal_printf.c

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/*
* Minimal vsnprintf(), snprintf(), sprintf(), and sscanf() for Duktape.
* The supported conversion formats narrowly match what Duktape needs.
*/
#include <stdarg.h> /* va_list etc */
#include <stddef.h> /* size_t */
#include <stdint.h> /* SIZE_MAX */
/* Write character with bound checking. Offset 'off' is updated regardless
* of whether an actual write is made. This is necessary to satisfy snprintf()
* return value semantics.
*/
#define DUK__WRITE_CHAR(c) do { \
if (off < size) { \
str[off] = (char) c; \
} \
off++; \
} while (0)
/* Digits up to radix 16. */
static const char duk__format_digits[16] = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
};
/* Format an unsigned long with various options. An unsigned long is large
* enough for formatting all supported types.
*/
static size_t duk__format_long(char *str,
size_t size,
size_t off,
int fixed_length,
char pad,
int radix,
int neg_sign,
unsigned long v) {
char buf[24]; /* 2^64 = 18446744073709552000, length 20 */
char *required;
char *p;
int i;
/* Format in reverse order first. Ensure at least one digit is output
* to handle '0' correctly. Note that space padding and zero padding
* handle negative sign differently:
*
* %9d and -321 => ' -321'
* %09d and -321 => '-00000321'
*/
for (i = 0; i < (int) sizeof(buf); i++) {
buf[i] = pad; /* compiles into memset() equivalent, avoid memset() dependency */
}
p = buf;
do {
*p++ = duk__format_digits[v % radix];
v /= radix;
} while (v != 0);
required = buf + fixed_length;
if (p < required && pad == (char) '0') {
/* Zero padding and we didn't reach maximum length: place
* negative sign at the last position. We can't get here
* with fixed_length == 0 so that required[-1] is safe.
*
* Technically we should only do this for 'neg_sign == 1',
* but it's OK to advance the pointer even when that's not
* the case.
*/
p = required - 1;
}
if (neg_sign) {
*p++ = (char) '-';
}
if (p < required) {
p = required;
}
/* Now [buf,p[ contains the result in reverse; copy into place. */
while (p > buf) {
p--;
DUK__WRITE_CHAR(*p);
}
return off;
}
/* Parse a pointer. Must parse whatever is produced by '%p' in sprintf(). */
static int duk__parse_pointer(const char *str, void **out) {
const unsigned char *p;
unsigned char ch;
int count;
int limit;
long val; /* assume void * fits into long */
/* We only need to parse what our minimal printf() produces, so that
* we can check for a '0x' prefix, and assume all hex digits are
* lowercase.
*/
p = (const unsigned char *) str;
if (p[0] != (unsigned char) '0' || p[1] != (unsigned char) 'x') {
return 0;
}
p += 2;
for (val = 0, count = 0, limit = sizeof(void *) * 2; count < limit; count++) {
ch = *p++;
val <<= 4;
if (ch >= (unsigned char) '0' && ch <= (unsigned char) '9') {
val += ch - (unsigned char) '0';
} else if (ch >= (unsigned char) 'a' && ch <= (unsigned char) 'f') {
val += ch - (unsigned char) 'a' + 0x0a;
} else {
return 0;
}
}
/* The input may end at a NUL or garbage may follow. As long as we
* parse the '%p' correctly, garbage is allowed to follow, and the
* JX pointer parsing also relies on that.
*/
*out = (void *) val;
return 1;
}
/* Minimal vsnprintf() entry point. */
int duk_minimal_vsnprintf(char *str, size_t size, const char *format, va_list ap) {
size_t off = 0;
const char *p;
#if 0
const char *p_tmp;
const char *p_fmt_start;
#endif
char c;
char pad;
int fixed_length;
int is_long;
/* Assume str != NULL unless size == 0.
* Assume format != NULL.
*/
p = format;
for (;;) {
c = *p++;
if (c == (char) 0) {
break;
}
if (c != (char) '%') {
DUK__WRITE_CHAR(c);
continue;
}
/* Start format sequence. Scan flags and format specifier. */
#if 0
p_fmt_start = p - 1;
#endif
is_long = 0;
pad = ' ';
fixed_length = 0;
for (;;) {
c = *p++;
if (c == (char) 'l') {
is_long = 1;
} else if (c == (char) '0') {
/* Only support pad character '0'. */
pad = '0';
} else if (c >= (char) '1' && c <= (char) '9') {
/* Only support fixed lengths 1-9. */
fixed_length = (int) (c - (char) '0');
} else if (c == (char) 'd') {
long v;
int neg_sign = 0;
if (is_long) {
v = va_arg(ap, long);
} else {
v = (long) va_arg(ap, int);
}
if (v < 0) {
neg_sign = 1;
v = -v;
}
off = duk__format_long(str, size, off, fixed_length, pad, 10, neg_sign, (unsigned long) v);
break;
} else if (c == (char) 'u') {
unsigned long v;
if (is_long) {
v = va_arg(ap, unsigned long);
} else {
v = (unsigned long) va_arg(ap, unsigned int);
}
off = duk__format_long(str, size, off, fixed_length, pad, 10, 0, v);
break;
} else if (c == (char) 'x') {
unsigned long v;
if (is_long) {
v = va_arg(ap, unsigned long);
} else {
v = (unsigned long) va_arg(ap, unsigned int);
}
off = duk__format_long(str, size, off, fixed_length, pad, 16, 0, v);
break;
} else if (c == (char) 'c') {
char v;
v = (char) va_arg(ap, int); /* intentionally not 'char' */
DUK__WRITE_CHAR(v);
break;
} else if (c == (char) 's') {
const char *v;
char c_tmp;
v = va_arg(ap, const char *);
if (v) {
for (;;) {
c_tmp = *v++;
if (c_tmp) {
DUK__WRITE_CHAR(c_tmp);
} else {
break;
}
}
}
break;
} else if (c == (char) 'p') {
/* Assume a void * can be represented by 'long'. This is not
* always the case. NULL pointer is printed out as 0x0000...
*/
void *v;
v = va_arg(ap, void *);
DUK__WRITE_CHAR('0');
DUK__WRITE_CHAR('x');
off = duk__format_long(str, size, off, sizeof(void *) * 2, '0', 16, 0, (unsigned long) v);
break;
} else {
/* Unrecognized, bail out early. We could also emit the format
* specifier verbatim, but it'd be a waste of footprint because
* this case should never happen in practice.
*/
#if 0
DUK__WRITE_CHAR('!');
#endif
#if 0
for (p_tmp = p_fmt_start; p_tmp != p; p_tmp++) {
DUK__WRITE_CHAR(*p_tmp);
}
break;
#endif
goto finish;
}
}
}
finish:
if (off < size) {
str[off] = (char) 0; /* No increment for 'off', not counted in return value. */
} else if (size > 0) {
/* Forced termination. */
str[size - 1] = 0;
}
return (int) off;
}
/* Minimal snprintf() entry point. */
int duk_minimal_snprintf(char *str, size_t size, const char *format, ...) {
va_list ap;
int ret;
va_start(ap, format);
ret = duk_minimal_vsnprintf(str, size, format, ap);
va_end(ap);
return ret;
}
/* Minimal sprintf() entry point. */
int duk_minimal_sprintf(char *str, const char *format, ...) {
va_list ap;
int ret;
va_start(ap, format);
ret = duk_minimal_vsnprintf(str, SIZE_MAX, format, ap);
va_end(ap);
return ret;
}
/* Minimal sscanf() entry point. */
int duk_minimal_sscanf(const char *str, const char *format, ...) {
va_list ap;
int ret;
void **out;
/* Only the exact "%p" format is supported. */
if (format[0] != (char) '%' ||
format[1] != (char) 'p' ||
format[2] != (char) 0) {
}
va_start(ap, format);
out = va_arg(ap, void **);
ret = duk__parse_pointer(str, out);
va_end(ap);
return ret;
}
#undef DUK__WRITE_CHAR