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