/** * Copyright (c) 2014-2019 Marco Paland * * Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on * embedded systems with a very limited resources. These routines are thread * safe and reentrant! * * Author: Marco Paland (info@paland.com) PALANDesign Hannover, Germany */ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include #include #include #include #include // import float.h for DBL_MAX #ifdef ENABLE_FLOAT #include #endif // 'ntoa' conversion buffer size, this must be big enough to hold one converted // numeric number including padded zeros (dynamically created on stack) #define PRINTF_NTOA_BUFFER_SIZE 32u // 'ftoa' conversion buffer size, this must be big enough to hold one converted // float number including padded zeros (dynamically created on stack) #define PRINTF_FTOA_BUFFER_SIZE 32u // define the default floating point precision #define PRINTF_DEFAULT_FLOAT_PRECISION 6u // define the largest float suitable to print with %f #define PRINTF_MAX_FLOAT 1e9 // internal flag definitions #define FLAGS_ZEROPAD (1u << 0u) #define FLAGS_LEFT (1u << 1u) #define FLAGS_PLUS (1u << 2u) #define FLAGS_SPACE (1u << 3u) #define FLAGS_HASH (1u << 4u) #define FLAGS_UPPERCASE (1u << 5u) #define FLAGS_CHAR (1u << 6u) #define FLAGS_SHORT (1u << 7u) #define FLAGS_LONG (1u << 8u) #define FLAGS_LONG_LONG (1u << 9u) #define FLAGS_PRECISION (1u << 10u) #define FLAGS_ADAPT_EXP (1u << 11u) #define FLAGS_CUSTOM (1u << 12u) // output function type typedef void (*out_fct_type)(char character, void* buffer, size_t idx, size_t maxlen); // wrapper (used as buffer) for output function type typedef struct { void (*fct)(char character, void* arg); void* arg; } out_fct_wrap_type; static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va); static inline void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen); static inline void _out_null(char character, void* buffer, size_t idx, size_t maxlen); static inline void _out_fct(char character, void* buffer, size_t idx, size_t maxlen); static unsigned int _atoi(const char** str); static size_t _out_rev(out_fct_type out, char* buffer, size_t idx, size_t maxlen, const char* buf, size_t len, unsigned int width, unsigned int flags); static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags); static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags); static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags); #ifdef ENABLE_BLOAT static char _custom(unsigned int flags, size_t *index); #endif // ENABLE_BLOAT #ifdef ENABLE_FLOAT static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags); static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags); #endif // ENABLE_FLOAT /******************************* * Implementations: public API * *******************************/ int kernaux_printf(void (*out)(char character, void* arg), void* arg, const char* format, ...) { va_list va; va_start(va, format); const out_fct_wrap_type out_fct_wrap = { out, arg }; const int ret = _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va); va_end(va); return ret; } int kernaux_vprintf(void (*out)(char character, void* arg), void* arg, const char* format, va_list va) { const out_fct_wrap_type out_fct_wrap = { out, arg }; return _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va); } int kernaux_snprintf(char* buffer, size_t count, const char* format, ...) { va_list va; va_start(va, format); const int ret = _vsnprintf(_out_buffer, buffer, count, format, va); va_end(va); return ret; } int kernaux_vsnprintf(char* buffer, size_t count, const char* format, va_list va) { return _vsnprintf(_out_buffer, buffer, count, format, va); } int kernaux_sprintf(char* buffer, const char* format, ...) { va_list va; va_start(va, format); const int ret = _vsnprintf(_out_buffer, buffer, (size_t)-1, format, va); va_end(va); return ret; } /****************************************** * Implementation: main internal function * ******************************************/ int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va) { unsigned int flags, width, precision, n; size_t idx = 0u; if (!buffer) { // use null output function out = _out_null; } while (*format) { // format specifier? %[flags][width][.precision][length] if (*format != '%') { // no out(*format, buffer, idx++, maxlen); format++; continue; } else { // yes, evaluate it format++; } // evaluate flags flags = 0u; do { switch (*format) { case '0': flags |= FLAGS_ZEROPAD; format++; n = 1u; break; case '-': flags |= FLAGS_LEFT; format++; n = 1u; break; case '+': flags |= FLAGS_PLUS; format++; n = 1u; break; case ' ': flags |= FLAGS_SPACE; format++; n = 1u; break; case '#': flags |= FLAGS_HASH; format++; n = 1u; break; default: n = 0u; break; } } while (n); // evaluate width field width = 0u; if (isdigit(*format)) { width = _atoi(&format); } else if (*format == '*') { const int w = va_arg(va, int); if (w < 0) { flags |= FLAGS_LEFT; // reverse padding width = (unsigned int)-w; } else { width = (unsigned int)w; } format++; } // evaluate precision field precision = 0u; if (*format == '.') { flags |= FLAGS_PRECISION; format++; if (isdigit(*format)) { precision = _atoi(&format); } else if (*format == '*') { const int prec = (int)va_arg(va, int); precision = prec > 0 ? (unsigned int)prec : 0u; format++; } } // evaluate length field switch (*format) { case 'l': flags |= FLAGS_LONG; format++; if (*format == 'l') { flags |= FLAGS_LONG_LONG; format++; } break; case 'h': flags |= FLAGS_SHORT; format++; if (*format == 'h') { flags |= FLAGS_CHAR; format++; } break; case 't': flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG); format++; break; case 'j': flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG); format++; break; case 'z': flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG); format++; break; #ifdef ENABLE_BLOAT case 'S': if (*(++format) == 'U') { flags |= FLAGS_CUSTOM; ++format; } else { --format; } break; #endif // ENABLE_BLOAT default: break; } // evaluate specifier switch (*format) { case 'd': case 'i': case 'u': case 'x': case 'X': case 'o': case 'b': { // set the base unsigned int base; if (*format == 'x' || *format == 'X') { base = 16u; } else if (*format == 'o') { base = 8u; } else if (*format == 'b') { base = 2u; } else { base = 10u; flags &= ~FLAGS_HASH; // no hash for dec format } // uppercase if (*format == 'X') { flags |= FLAGS_UPPERCASE; } // no plus or space flag for u, x, X, o, b if ((*format != 'i') && (*format != 'd')) { flags &= ~(FLAGS_PLUS | FLAGS_SPACE); } // ignore '0' flag when precision is given if (flags & FLAGS_PRECISION) { flags &= ~FLAGS_ZEROPAD; } // convert the integer if ((*format == 'i') || (*format == 'd')) { // signed if (flags & FLAGS_LONG_LONG) { const long long value = va_arg(va, long long); idx = _ntoa_long_long(out, buffer, idx, maxlen, (unsigned long long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags); } else if (flags & FLAGS_LONG) { const long value = va_arg(va, long); idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags); } else { const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int); idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags); } } else { // unsigned if (flags & FLAGS_LONG_LONG) { idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base, precision, width, flags); } else if (flags & FLAGS_LONG) { idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision, width, flags); } else { const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char)va_arg(va, unsigned int) : (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(va, unsigned int) : va_arg(va, unsigned int); idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags); } } format++; break; } #ifdef ENABLE_FLOAT case 'f': case 'F': if (*format == 'F') flags |= FLAGS_UPPERCASE; idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags); format++; break; case 'e': case 'E': case 'g': case 'G': if ((*format == 'g')||(*format == 'G')) flags |= FLAGS_ADAPT_EXP; if ((*format == 'E')||(*format == 'G')) flags |= FLAGS_UPPERCASE; idx = _etoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags); format++; break; #endif // ENABLE_FLOAT case 'c': { unsigned int l = 1u; // pre padding if (!(flags & FLAGS_LEFT)) { while (l++ < width) { out(' ', buffer, idx++, maxlen); } } // char output out((char)va_arg(va, int), buffer, idx++, maxlen); // post padding if (flags & FLAGS_LEFT) { while (l++ < width) { out(' ', buffer, idx++, maxlen); } } format++; break; } case 's': { const char* p = va_arg(va, char*); unsigned int l = strnlen(p, precision ? precision : (size_t)-1); // pre padding if (flags & FLAGS_PRECISION) { l = (l < precision ? l : precision); } if (!(flags & FLAGS_LEFT)) { while (l++ < width) { out(' ', buffer, idx++, maxlen); } } // string output while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) { out(*(p++), buffer, idx++, maxlen); } // post padding if (flags & FLAGS_LEFT) { while (l++ < width) { out(' ', buffer, idx++, maxlen); } } format++; break; } #ifdef ENABLE_BLOAT case 'S': if (flags & FLAGS_CUSTOM) { format++; size_t index = 0; char c; while ((c = _custom(flags, &index))) { out(c, buffer, idx++, maxlen); } } break; #endif // ENABLE_BLOAT case 'p': { width = sizeof(void*) * 2u; flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE; const bool is_ll = sizeof(uintptr_t) == sizeof(long long); if (is_ll) { idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16u, precision, width, flags); } else { idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16u, precision, width, flags); } format++; break; } case '%': out('%', buffer, idx++, maxlen); format++; break; default: out(*format, buffer, idx++, maxlen); format++; break; } } // termination out((char)0, buffer, idx < maxlen ? idx : maxlen - 1u, maxlen); // return written chars without terminating \0 return (int)idx; } /************************************* * Implementations: helper functions * *************************************/ // internal buffer output void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen) { if (idx < maxlen) { ((char*)buffer)[idx] = character; } } // internal null output void _out_null(char character, void* buffer, size_t idx, size_t maxlen) { (void)character; (void)buffer; (void)idx; (void)maxlen; } // internal output function wrapper void _out_fct(char character, void* buffer, size_t idx, size_t maxlen) { (void)idx; (void)maxlen; if (character) { // buffer is the output fct pointer ((out_fct_wrap_type*)buffer)->fct(character, ((out_fct_wrap_type*)buffer)->arg); } } // internal ASCII string to unsigned int conversion unsigned int _atoi(const char** str) { const int result = atoi(*str); while (isdigit(**str)) (*str)++; return result; } // output the specified string in reverse, taking care of any zero-padding size_t _out_rev(out_fct_type out, char* buffer, size_t idx, size_t maxlen, const char* buf, size_t len, unsigned int width, unsigned int flags) { const size_t start_idx = idx; // pad spaces up to given width if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) { for (size_t i = len; i < width; i++) { out(' ', buffer, idx++, maxlen); } } // reverse string while (len) { out(buf[--len], buffer, idx++, maxlen); } // append pad spaces up to given width if (flags & FLAGS_LEFT) { while (idx - start_idx < width) { out(' ', buffer, idx++, maxlen); } } return idx; } // internal itoa format size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags) { // pad leading zeros if (!(flags & FLAGS_LEFT)) { if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) { width--; } while ((len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) { buf[len++] = '0'; } while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) { buf[len++] = '0'; } } // handle hash if (flags & FLAGS_HASH) { if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) { len--; if (len && (base == 16u)) { len--; } } if ((base == 16u) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) { buf[len++] = 'x'; } else if ((base == 16u) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) { buf[len++] = 'X'; } else if ((base == 2u) && (len < PRINTF_NTOA_BUFFER_SIZE)) { buf[len++] = 'b'; } if (len < PRINTF_NTOA_BUFFER_SIZE) { buf[len++] = '0'; } } if (len < PRINTF_NTOA_BUFFER_SIZE) { if (negative) { buf[len++] = '-'; } else if (flags & FLAGS_PLUS) { buf[len++] = '+'; // ignore the space if the '+' exists } else if (flags & FLAGS_SPACE) { buf[len++] = ' '; } } return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags); } // internal itoa for 'long' type size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags) { char buf[PRINTF_NTOA_BUFFER_SIZE]; size_t len = 0u; // no hash for 0 values if (!value) { flags &= ~FLAGS_HASH; } // write if precision != 0 and value is != 0 if (!(flags & FLAGS_PRECISION) || value) { do { const char digit = (char)(value % base); buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10; value /= base; } while (value && (len < PRINTF_NTOA_BUFFER_SIZE)); } return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags); } // internal itoa for 'long long' type size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags) { char buf[PRINTF_NTOA_BUFFER_SIZE]; size_t len = 0u; // no hash for 0 values if (!value) { flags &= ~FLAGS_HASH; } // write if precision != 0 and value is != 0 if (!(flags & FLAGS_PRECISION) || value) { do { const char digit = (char)(value % base); buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10; value /= base; } while (value && (len < PRINTF_NTOA_BUFFER_SIZE)); } return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags); } #ifdef ENABLE_BLOAT /** * Idea: superleaf1995 * Implementation: smwmaster */ static const char *const map = "\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xD3\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF7\xFE\xF7\xF7\xF9\xF7" "\xFE\xF5\xF5\xF9\xF7\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF7\xE2\xA1\x96\x96\x96\x96\x96\xB2\xBD" "\xB6\xE3\xF5\xFE\xF9\xF9\xF9\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF7\xE2\x81\x81\x92\xE9\x96\x96\xE9\xE9\x92\x97\x97\x96" "\xFE\xFE\xF7\xF9\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF7\xF7\xE9\xB5\xF7\xE2\xB5\xB6\xA1\xA1\xA1\xB5\xE2\xE3\x81\x92\xF5\xF7" "\xF9\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF7\xB2\x97" "\xB2\xF7\xF7\xE2\xBA\xBA\xE3\xE2\xF5\xFE\xE2\x81\x97\xE9\xF7\xF7\xF9\xF9" "\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xBA\x81\x97\x97\x97\x96" "\xA1\xBD\xBD\xA1\xB2\xE9\x97\x97\x97\x97\x97\xB5\xF7\xF9\xF9\xD3\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF7\x92\x97\x97\x97\x97\x97\x97\x97\x97" "\x97\x97\x97\x97\x97\x97\x97\x97\xA1\xF7\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xBA\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97" "\x97\x97\x97\x97\x97\xE9\xF7\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\x96\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97" "\x97\x97\x92\xF7\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xFE\x81" "\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x81" "\xFE\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xB5\x97\x97\x97\x97" "\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\x97\xF5\xF9\xF9" "\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF7\x96\x97\x97\x97\xA1\xF5\xF9\xF9" "\xF9\xF9\xF9\xF9\xFE\x96\x97\x97\x97\x97\x97\x97\xE3\xF9\xF9\xD3\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF7\xF5\x81\x97\x97\x92\xF7\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xFE\x81\x97\x97\x97\x97\x97\xBA\xF9\xF9\xD3\xF9\xF9\xF7\xE2\xBA" "\xBA\xBA\xF5\xB2\x97\x97\x97\x97\xE3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF5" "\x81\x97\x97\x97\x97\x97\xE3\xF9\xF9\xD3\xF9\xF9\xFE\xE9\x81\x97\x97\x97" "\x97\x97\x81\x92\xB2\xF7\xF9\xF9\xF9\xF9\xF9\xF7\xF7\xF7\xB6\x97\x97\x97" "\x97\x97\x97\xE2\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF7\xFE\xB2\x92\x81\x81\x97\x97\x97\x97\x97\x97\xE9" "\xF7\xF9\xF9\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF5\xB2\x96\xE9\xE9\x96\xA1\xBD\xF5\xF9\xF9\xF9\xF9\xF9" "\xD3\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9" "\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xF9\xD3\xD3\xD9" "\xD9\xD9\xC1\x04&&i\x05&&i\x05&&\xC9\x04&&i\x05&&i\x05&&i\x05&&i\x05&&i" "\x05&&i\x05&&i\x05&&\xD1\x04&&i\x05&&\xD9\x04&&i\x05&&i\x05&&)\x05&&\xFB" "\x06&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05" "&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&-\x05&&" "\xD1\x06&&-\x05&&\xCA\x04&&-\x05&&"; char _custom(const unsigned int flags, size_t *const index) { return map[(*index)++] ^ (73 + ((flags >> 8) | 128)); } #endif // ENABLE_BLOAT #ifdef ENABLE_FLOAT // internal ftoa for fixed decimal floating point size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags) { char buf[PRINTF_FTOA_BUFFER_SIZE]; size_t len = 0u; double diff = 0.0; // powers of 10 static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 }; // test for special values if (value != value) return _out_rev(out, buffer, idx, maxlen, "nan", 3, width, flags); if (value < -DBL_MAX) return _out_rev(out, buffer, idx, maxlen, "fni-", 4, width, flags); if (value > DBL_MAX) return _out_rev(out, buffer, idx, maxlen, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4u : 3u, width, flags); // test for very large values // standard printf behavior is to print EVERY whole number digit -- which could be 100s of characters overflowing your buffers == bad if ((value > PRINTF_MAX_FLOAT) || (value < -PRINTF_MAX_FLOAT)) { return _etoa(out, buffer, idx, maxlen, value, prec, width, flags); } // test for negative bool negative = false; if (value < 0) { negative = true; value = 0 - value; } // set default precision, if not set explicitly if (!(flags & FLAGS_PRECISION)) { prec = PRINTF_DEFAULT_FLOAT_PRECISION; } // limit precision to 9, cause a prec >= 10 can lead to overflow errors while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9u)) { buf[len++] = '0'; prec--; } int whole = (int)value; double tmp = (value - whole) * pow10[prec]; unsigned long frac = (unsigned long)tmp; diff = tmp - frac; if (diff > 0.5) { ++frac; // handle rollover, e.g. case 0.99 with prec 1 is 1.0 if (frac >= pow10[prec]) { frac = 0; ++whole; } } else if (diff < 0.5) { // TODO: do nothing? } else if ((frac == 0u) || (frac & 1u)) { // if halfway, round up if odd OR if last digit is 0 ++frac; } if (prec == 0u) { diff = value - (double)whole; if ((!(diff < 0.5) || (diff > 0.5)) && (whole & 1)) { // exactly 0.5 and ODD, then round up // 1.5 -> 2, but 2.5 -> 2 ++whole; } } else { unsigned int count = prec; // now do fractional part, as an unsigned number while (len < PRINTF_FTOA_BUFFER_SIZE) { --count; buf[len++] = (char)(48u + (frac % 10u)); if (!(frac /= 10u)) { break; } } // add extra 0s while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0u)) { buf[len++] = '0'; } if (len < PRINTF_FTOA_BUFFER_SIZE) { // add decimal buf[len++] = '.'; } } // do whole part, number is reversed while (len < PRINTF_FTOA_BUFFER_SIZE) { buf[len++] = (char)(48 + (whole % 10)); if (!(whole /= 10)) { break; } } // pad leading zeros if (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD)) { if (width && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) { width--; } while ((len < width) && (len < PRINTF_FTOA_BUFFER_SIZE)) { buf[len++] = '0'; } } if (len < PRINTF_FTOA_BUFFER_SIZE) { if (negative) { buf[len++] = '-'; } else if (flags & FLAGS_PLUS) { buf[len++] = '+'; // ignore the space if the '+' exists } else if (flags & FLAGS_SPACE) { buf[len++] = ' '; } } return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags); } // internal ftoa variant for exponential floating-point type, contributed by Martijn Jasperse size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags) { // check for NaN and special values if ((value != value) || (value > DBL_MAX) || (value < -DBL_MAX)) { return _ftoa(out, buffer, idx, maxlen, value, prec, width, flags); } // determine the sign const bool negative = value < 0; if (negative) { value = -value; } // default precision if (!(flags & FLAGS_PRECISION)) { prec = PRINTF_DEFAULT_FLOAT_PRECISION; } // determine the decimal exponent // based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c) union { uint64_t U; double F; } conv; conv.F = value; int exp2 = (int)((conv.U >> 52u) & 0x07FFU) - 1023; // effectively log2 conv.U = (conv.U & ((1ull << 52u) - 1u)) | (102ull << 52u); // drop the exponent so conv.F is now in [1,2) // now approximate log10 from the log2 integer part and an expansion of ln around 1.5 int expval = (int)(0.1760912590558 + exp2 * 0.301029995663981 + (conv.F - 1.5) * 0.289529654602168); // now we want to compute 10^expval but we want to be sure it won't overflow exp2 = (int)(expval * 3.321928094887362 + 0.5); const double z = expval * 2.302585092994046 - exp2 * 0.6931471805599453; const double z2 = z * z; conv.U = (uint64_t)(exp2 + 1023) << 52u; // compute exp(z) using continued fractions, see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex conv.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14))))); // correct for rounding errors if (value < conv.F) { expval--; conv.F /= 10; } // the exponent format is "%+03d" and largest value is "307", so set aside 4-5 characters unsigned int minwidth = ((expval < 100) && (expval > -100)) ? 4u : 5u; // in "%g" mode, "prec" is the number of *significant figures* not decimals if (flags & FLAGS_ADAPT_EXP) { // do we want to fall-back to "%f" mode? if ((value >= 1e-4) && (value < 1e6)) { if ((int)prec > expval) { prec = (unsigned)((int)prec - expval - 1); } else { prec = 0; } flags |= FLAGS_PRECISION; // make sure _ftoa respects precision // no characters in exponent minwidth = 0u; expval = 0; } else { // we use one sigfig for the whole part if ((prec > 0) && (flags & FLAGS_PRECISION)) { --prec; } } } // will everything fit? unsigned int fwidth = width; if (width > minwidth) { // we didn't fall-back so subtract the characters required for the exponent fwidth -= minwidth; } else { // not enough characters, so go back to default sizing fwidth = 0u; } if ((flags & FLAGS_LEFT) && minwidth) { // if we're padding on the right, DON'T pad the floating part fwidth = 0u; } // rescale the float value if (expval) { value /= conv.F; } // output the floating part const size_t start_idx = idx; idx = _ftoa(out, buffer, idx, maxlen, negative ? -value : value, prec, fwidth, flags & ~FLAGS_ADAPT_EXP); // output the exponent part if (minwidth) { // output the exponential symbol out((flags & FLAGS_UPPERCASE) ? 'E' : 'e', buffer, idx++, maxlen); // output the exponent value idx = _ntoa_long(out, buffer, idx, maxlen, (expval < 0) ? -expval : expval, expval < 0, 10, 0, minwidth-1, FLAGS_ZEROPAD | FLAGS_PLUS); // might need to right-pad spaces if (flags & FLAGS_LEFT) { while (idx - start_idx < width) out(' ', buffer, idx++, maxlen); } } return idx; } #endif // ENABLE_FLOAT