Sylvain Munaut | 26bc465 | 2020-09-14 10:19:49 +0200 | [diff] [blame] | 1 | /* |
| 2 | * The Minimal snprintf() implementation |
| 3 | * |
| 4 | * Copyright (c) 2013,2014 Michal Ludvig <michal@logix.cz> |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions are met: |
| 9 | * * Redistributions of source code must retain the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer. |
| 11 | * * Redistributions in binary form must reproduce the above copyright |
| 12 | * notice, this list of conditions and the following disclaimer in the |
| 13 | * documentation and/or other materials provided with the distribution. |
| 14 | * * Neither the name of the auhor nor the names of its contributors |
| 15 | * may be used to endorse or promote products derived from this software |
| 16 | * without specific prior written permission. |
| 17 | * |
| 18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND |
| 19 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| 20 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| 21 | * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| 22 | * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| 23 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| 24 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| 25 | * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 26 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| 27 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 28 | * |
| 29 | * ---- |
| 30 | * |
| 31 | * This is a minimal snprintf() implementation optimised |
| 32 | * for embedded systems with a very limited program memory. |
| 33 | * mini_snprintf() doesn't support _all_ the formatting |
| 34 | * the glibc does but on the other hand is a lot smaller. |
| 35 | * Here are some numbers from my STM32 project (.bin file size): |
| 36 | * no snprintf(): 10768 bytes |
| 37 | * mini snprintf(): 11420 bytes (+ 652 bytes) |
| 38 | * glibc snprintf(): 34860 bytes (+24092 bytes) |
| 39 | * Wasting nearly 24kB of memory just for snprintf() on |
| 40 | * a chip with 32kB flash is crazy. Use mini_snprintf() instead. |
| 41 | * |
| 42 | */ |
| 43 | |
| 44 | #include "mini-printf.h" |
| 45 | |
| 46 | static unsigned int |
| 47 | mini_strlen(const char *s) |
| 48 | { |
| 49 | unsigned int len = 0; |
| 50 | while (s[len] != '\0') len++; |
| 51 | return len; |
| 52 | } |
| 53 | |
| 54 | static unsigned int |
| 55 | mini_itoa(int value, unsigned int radix, unsigned int uppercase, unsigned int unsig, |
| 56 | char *buffer, unsigned int zero_pad) |
| 57 | { |
| 58 | char *pbuffer = buffer; |
| 59 | int negative = 0; |
| 60 | unsigned int i, len; |
| 61 | |
| 62 | /* No support for unusual radixes. */ |
| 63 | if (radix > 16) |
| 64 | return 0; |
| 65 | |
| 66 | if (value < 0 && !unsig) { |
| 67 | negative = 1; |
| 68 | value = -value; |
| 69 | } |
| 70 | |
| 71 | /* This builds the string back to front ... */ |
| 72 | do { |
| 73 | int digit = value % radix; |
| 74 | *(pbuffer++) = (digit < 10 ? '0' + digit : (uppercase ? 'A' : 'a') + digit - 10); |
| 75 | value /= radix; |
| 76 | } while (value > 0); |
| 77 | |
| 78 | for (i = (pbuffer - buffer); i < zero_pad; i++) |
| 79 | *(pbuffer++) = '0'; |
| 80 | |
| 81 | if (negative) |
| 82 | *(pbuffer++) = '-'; |
| 83 | |
| 84 | *(pbuffer) = '\0'; |
| 85 | |
| 86 | /* ... now we reverse it (could do it recursively but will |
| 87 | * conserve the stack space) */ |
| 88 | len = (pbuffer - buffer); |
| 89 | for (i = 0; i < len / 2; i++) { |
| 90 | char j = buffer[i]; |
| 91 | buffer[i] = buffer[len-i-1]; |
| 92 | buffer[len-i-1] = j; |
| 93 | } |
| 94 | |
| 95 | return len; |
| 96 | } |
| 97 | |
| 98 | struct mini_buff { |
| 99 | char *buffer, *pbuffer; |
| 100 | unsigned int buffer_len; |
| 101 | }; |
| 102 | |
| 103 | static int |
| 104 | _putc(int ch, struct mini_buff *b) |
| 105 | { |
| 106 | if ((unsigned int)((b->pbuffer - b->buffer) + 1) >= b->buffer_len) |
| 107 | return 0; |
| 108 | *(b->pbuffer++) = ch; |
| 109 | *(b->pbuffer) = '\0'; |
| 110 | return 1; |
| 111 | } |
| 112 | |
| 113 | static int |
| 114 | _puts(char *s, unsigned int len, struct mini_buff *b) |
| 115 | { |
| 116 | unsigned int i; |
| 117 | |
| 118 | if (b->buffer_len - (b->pbuffer - b->buffer) - 1 < len) |
| 119 | len = b->buffer_len - (b->pbuffer - b->buffer) - 1; |
| 120 | |
| 121 | /* Copy to buffer */ |
| 122 | for (i = 0; i < len; i++) |
| 123 | *(b->pbuffer++) = s[i]; |
| 124 | *(b->pbuffer) = '\0'; |
| 125 | |
| 126 | return len; |
| 127 | } |
| 128 | |
| 129 | int |
| 130 | mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list va) |
| 131 | { |
| 132 | struct mini_buff b; |
| 133 | char bf[24]; |
| 134 | char ch; |
| 135 | |
| 136 | b.buffer = buffer; |
| 137 | b.pbuffer = buffer; |
| 138 | b.buffer_len = buffer_len; |
| 139 | |
| 140 | while ((ch=*(fmt++))) { |
| 141 | if ((unsigned int)((b.pbuffer - b.buffer) + 1) >= b.buffer_len) |
| 142 | break; |
| 143 | if (ch!='%') |
| 144 | _putc(ch, &b); |
| 145 | else { |
| 146 | char zero_pad = 0; |
| 147 | char *ptr; |
| 148 | unsigned int len; |
| 149 | |
| 150 | ch=*(fmt++); |
| 151 | |
| 152 | /* Zero padding requested */ |
| 153 | if (ch=='0') { |
| 154 | ch=*(fmt++); |
| 155 | if (ch == '\0') |
| 156 | goto end; |
| 157 | if (ch >= '0' && ch <= '9') |
| 158 | zero_pad = ch - '0'; |
| 159 | ch=*(fmt++); |
| 160 | } |
| 161 | |
| 162 | switch (ch) { |
| 163 | case 0: |
| 164 | goto end; |
| 165 | |
| 166 | case 'u': |
| 167 | case 'd': |
| 168 | len = mini_itoa(va_arg(va, unsigned int), 10, 0, (ch=='u'), bf, zero_pad); |
| 169 | _puts(bf, len, &b); |
| 170 | break; |
| 171 | |
| 172 | case 'x': |
| 173 | case 'X': |
| 174 | len = mini_itoa(va_arg(va, unsigned int), 16, (ch=='X'), 1, bf, zero_pad); |
| 175 | _puts(bf, len, &b); |
| 176 | break; |
| 177 | |
| 178 | case 'c' : |
| 179 | _putc((char)(va_arg(va, int)), &b); |
| 180 | break; |
| 181 | |
| 182 | case 's' : |
| 183 | ptr = va_arg(va, char*); |
| 184 | _puts(ptr, mini_strlen(ptr), &b); |
| 185 | break; |
| 186 | |
| 187 | default: |
| 188 | _putc(ch, &b); |
| 189 | break; |
| 190 | } |
| 191 | } |
| 192 | } |
| 193 | end: |
| 194 | return b.pbuffer - b.buffer; |
| 195 | } |
| 196 | |
| 197 | |
| 198 | int |
| 199 | mini_snprintf(char* buffer, unsigned int buffer_len, const char *fmt, ...) |
| 200 | { |
| 201 | int ret; |
| 202 | va_list va; |
| 203 | va_start(va, fmt); |
| 204 | ret = mini_vsnprintf(buffer, buffer_len, fmt, va); |
| 205 | va_end(va); |
| 206 | |
| 207 | return ret; |
| 208 | } |