FATFS 初学之 f_gets/ f_putc/ f_puts/ f_printf
2014-08-14 13:02 Danhuise 阅读(9821) 评论(0) 编辑 收藏 举报详见：嵌入式大讲堂
f_gets：
1 /*-----------------------------------------------------------------------*/ 2 /* Get a string from the file */ 3 /*-----------------------------------------------------------------------*/ 4 TCHAR* f_gets ( 5 TCHAR* buff, /* Pointer to the string buffer to read */ 6 int len, /* Size of string buffer (characters) */ 7 FIL* fil /* Pointer to the file object */ 8 ) 9 { 10 int n = 0; 11 TCHAR c, *p = buff; 12 BYTE s[2]; 13 UINT rc; 14 15 16 while (n < len - 1) { /* Read bytes until buffer gets filled */ 17 f_read(fil, s, 1, &rc); 18 if (rc != 1) break; /* Break on EOF or error */ 19 c = s[0]; 20 #if _LFN_UNICODE /* Read a character in UTF-8 encoding */ 21 if (c >= 0x80) { 22 if (c < 0xC0) continue; /* Skip stray trailer */ 23 if (c < 0xE0) { /* Two-byte sequense */ 24 f_read(fil, s, 1, &rc); 25 if (rc != 1) break; 26 c = ((c & 0x1F) << 6) | (s[0] & 0x3F); 27 if (c < 0x80) c = '?'; 28 } else { 29 if (c < 0xF0) { /* Three-byte sequense */ 30 f_read(fil, s, 2, &rc); 31 if (rc != 2) break; 32 c = (c << 12) | ((s[0] & 0x3F) << 6) | (s[1] & 0x3F); 33 if (c < 0x800) c = '?'; 34 } else { /* Reject four-byte sequense */ 35 c = '?'; 36 } 37 } 38 } 39 #endif 40 #if _USE_STRFUNC >= 2 41 if (c == '\r') continue; /* Strip '\r' */ 42 #endif 43 *p++ = c; 44 n++; 45 if (c == '\n') break; /* Break on EOL */ 46 } 47 *p = 0; 48 return n ? buff : 0; /* When no data read (eof or error), return with error. */ 49 }
函数功能：f_gets从文件中读取一个字符串。
描述：
f_gets函数当_USE_STRFUNC == 1或者_USE_STRFUNC == 2时可用。如果_USE_STRFUNC == 2，文件中包含的'\r'则被去除。
f_gets函数是f_read的一个封装函数。当读取到'\n'、文件结束或缓冲区被填冲了Size - 1个字符时，读操作结束。读取的字符串以'\0'结束。当文件结束或读操作中发生了任何错误，f_gets()返回一个空字符串。可以使用宏f_eof()和f_error()检查EOF和错误状态。
f_putc：
1 /*-----------------------------------------------------------------------*/ 2 /* Put a character to the file */ 3 /*-----------------------------------------------------------------------*/ 4 int f_putc ( 5 TCHAR c, /* A character to be output */ 6 FIL* fil /* Pointer to the file object */ 7 ) 8 { 9 UINT bw, btw; 10 BYTE s[3]; 11 12 13 #if _USE_STRFUNC >= 2 14 if (c == '\n') f_putc ('\r', fil); /* LF -> CRLF conversion */ 15 #endif 16 17 #if _LFN_UNICODE /* Write the character in UTF-8 encoding */ 18 if (c < 0x80) { /* 7-bit */ 19 s[0] = (BYTE)c; 20 btw = 1; 21 } else { 22 if (c < 0x800) { /* 11-bit */ 23 s[0] = (BYTE)(0xC0 | (c >> 6)); 24 s[1] = (BYTE)(0x80 | (c & 0x3F)); 25 btw = 2; 26 } else { /* 16-bit */ 27 s[0] = (BYTE)(0xE0 | (c >> 12)); 28 s[1] = (BYTE)(0x80 | ((c >> 6) & 0x3F)); 29 s[2] = (BYTE)(0x80 | (c & 0x3F)); 30 btw = 3; 31 } 32 } 33 #else /* Write the character without conversion */ 34 s[0] = (BYTE)c; 35 btw = 1; 36 #endif 37 f_write(fil, s, btw, &bw); /* Write the char to the file */ 38 return (bw == btw) ? 1 : EOF; /* Return the result */ 39 }
函数功能：f_putc函数向文件中写入一个字符。
描述：
f_putc函数当(_FS_READONLY == 0)&&(_USE_STRFUNC == 1 || _USE_STRFUNC == 2)时可用。当_USE_STRFUNC == 2时，字符'\n'被转换为"\r\n"写入文件中。
f_putc函数是f_write的一个封装函数。
f_puts：
1 /*-----------------------------------------------------------------------*/ 2 /* Put a string to the file */ 3 /*-----------------------------------------------------------------------*/ 4 int f_puts ( 5 const TCHAR* str, /* Pointer to the string to be output */ 6 FIL* fil /* Pointer to the file object */ 7 ) 8 { 9 int n; 10 11 12 for (n = 0; *str; str++, n++) { 13 if (f_putc(*str, fil) == EOF) return EOF; 14 } 15 return n; 16 }
函数功能：f_puts函数向文件中写入一个字符串。
描述：
f_puts()当(_FS_READONLY == 0)&&(_USE_STRFUNC == 1 || _USE_STRFUNC == 2)时可用。当_USE_STRFUNC == 2时，字符串中的'\n'被转换为"\r\n"写入文件中。
f_puts()是f_putc()的一个封装函数。
f_printf：
1 /*-----------------------------------------------------------------------*/ 2 /* Put a formatted string to the file */ 3 /*-----------------------------------------------------------------------*/ 4 int f_printf ( 5 FIL* fil, /* Pointer to the file object */ 6 const TCHAR* str, /* Pointer to the format string */ 7 ... /* Optional arguments... */ 8 ) 9 { 10 va_list arp; 11 BYTE f, r; 12 UINT i, j, w; 13 ULONG v; 14 TCHAR c, d, s[16], *p; 15 int res, chc, cc; 16 17 18 va_start(arp, str); 19 20 for (cc = res = 0; cc != EOF; res += cc) { 21 c = *str++; 22 if (c == 0) break; /* End of string */ 23 if (c != '%') { /* Non escape character */ 24 cc = f_putc(c, fil); 25 if (cc != EOF) cc = 1; 26 continue; 27 } 28 w = f = 0; 29 c = *str++; 30 if (c == '0') { /* Flag: '0' padding */ 31 f = 1; c = *str++; 32 } else { 33 if (c == '-') { /* Flag: left justified */ 34 f = 2; c = *str++; 35 } 36 } 37 while (IsDigit(c)) { /* Precision */ 38 w = w * 10 + c - '0'; 39 c = *str++; 40 } 41 if (c == 'l' || c == 'L') { /* Prefix: Size is long int */ 42 f |= 4; c = *str++; 43 } 44 if (!c) break; 45 d = c; 46 if (IsLower(d)) d -= 0x20; 47 switch (d) { /* Type is... */ 48 case 'S' : /* String */ 49 p = va_arg(arp, TCHAR*); 50 for (j = 0; p[j]; j++) ; 51 chc = 0; 52 if (!(f & 2)) { 53 while (j++ < w) chc += (cc = f_putc(' ', fil)); 54 } 55 chc += (cc = f_puts(p, fil)); 56 while (j++ < w) chc += (cc = f_putc(' ', fil)); 57 if (cc != EOF) cc = chc; 58 continue; 59 case 'C' : /* Character */ 60 cc = f_putc((TCHAR)va_arg(arp, int), fil); continue; 61 case 'B' : /* Binary */ 62 r = 2; break; 63 case 'O' : /* Octal */ 64 r = 8; break; 65 case 'D' : /* Signed decimal */ 66 case 'U' : /* Unsigned decimal */ 67 r = 10; break; 68 case 'X' : /* Hexdecimal */ 69 r = 16; break; 70 default: /* Unknown type (passthrough) */ 71 cc = f_putc(c, fil); continue; 72 } 73 74 /* Get an argument and put it in numeral */ 75 v = (f & 4) ? (ULONG)va_arg(arp, long) : ((d == 'D') ? (ULONG)(long)va_arg(arp, int) : (ULONG)va_arg(arp, unsigned int)); 76 if (d == 'D' && (v & 0x80000000)) { 77 v = 0 - v; 78 f |= 8; 79 } 80 i = 0; 81 do { 82 d = (TCHAR)(v % r); v /= r; 83 if (d > 9) d += (c == 'x') ? 0x27 : 0x07; 84 s[i++] = d + '0'; 85 } while (v && i < sizeof(s) / sizeof(s[0])); 86 if (f & 8) s[i++] = '-'; 87 j = i; d = (f & 1) ? '0' : ' '; 88 res = 0; 89 while (!(f & 2) && j++ < w) res += (cc = f_putc(d, fil)); 90 do res += (cc = f_putc(s[--i], fil)); while(i); 91 while (j++ < w) res += (cc = f_putc(' ', fil)); 92 if (cc != EOF) cc = res; 93 } 94 95 va_end(arp); 96 return (cc == EOF) ? cc : res; 97 }
函数功能：f_printf函数向文件中写入一个格式化字符串。
描述：
f_printf函数当(_FS_READONLY == 0)&&(_USE_STRFUNC == 1 || _USE_STRFUNC == 2)时可用。当_USE_STRFUNC == 2时，包含在格式化字符串中的'\n'将被转换成"\r\n"写入文件中。
f_printf函数是f_putc和f_puts的一个封装函数。
例：
1 f_gets(buf, NUM, &fil); // 从文件中读取一个字符串的前 NUM个字符 2 f_putc(ch, &fil); // 向文件中写入一个字符 3 f_puts((char *)buffer, &fil); // 向文件内写入一个字符串 4 5 f_printf(&fil, "%6d", -200); /* " -200" */ 6 f_printf(&fil, "%02u", 5); /* "05" */ 7 f_printf(&fil, "%ld", 12345678L); /* "12345678" */ 8 f_printf(&fil, "%08lX", 1194684UL); /* "00123ABC" */ 9 f_printf(&fil, "%s", "String"); /* "String" */ 10 f_printf(&fil, "%c", 'a'); /* "a" */
