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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <stddef.h>
  4. #include <ctype.h>
  5. #include <string.h>
  6. #include <errno.h>
  7.  
  8.  
  9. /* Position exactly to integer beginning */
  10. /* e.g. if you have: "str-str-3str "     */
  11. /* the returning pointer will point to:  */
  12. /* "-3str".                              */
  13. const char* getNumberPos(const char* str)
  14. {
  15.    const char* curChar = str;
  16.    /* Iterate through part of integer is there. */
  17.    while (   '\0' != curChar
  18.           && !(isdigit(*curChar) || '+' == *curChar || '-' == *curChar))
  19.    {
  20.       ++curChar;
  21.    }
  22.    /* Check if the sign is part of an integer, */
  23.    /* if not use this function recursive!      */
  24.    if ('+' == *curChar || '-' == *curChar)
  25.    {
  26.       const char* nextChar = curChar + 1;
  27.       if (   '\0' != *nextChar
  28.           && !isdigit(*nextChar))
  29.       {
  30.          ++curChar;
  31.          curChar = getNumberPos(curChar);
  32.       }
  33.    }
  34.    return curChar;
  35. }
  36.  
  37. /* Extended strtol function */
  38. long my_strtol(const char* str, char** endptr, int base)
  39. {
  40.    const char* curChar = getNumberPos(str);
  41.    return strtol(curChar, endptr, base);
  42. }
  43.  
  44.  
  45. int main()
  46. {
  47.    /* Loop index */
  48.    int idx;
  49.  
  50.    /* Declare and initialize char arrays. */
  51.    char array[]      = { "3" };
  52.    char arrayI[]     = { "    3   " };
  53.    char arrayII[]    = { "   -3   " };
  54.    char arrayIII[]   = { "str 3   " };
  55.    char arrayIV[]    = { "str-3   " };
  56.    char arrayV[]     = { "    3str" };
  57.    char arrayVI[]    = { "   -3str" };
  58.    char arrayVII[]   = { "str-3str" };
  59.    char arrayVIII[]  = { "s-r-3str" };
  60.  
  61.    /* Save each array in one array for iteration purposes. */
  62.    const char* const arrays[] = { array,
  63.                                   arrayI,
  64.                                   arrayII,
  65.                                   arrayIII,
  66.                                   arrayIV,
  67.                                   arrayV,
  68.                                   arrayVI,
  69.                                   arrayVII,
  70.                                   arrayVIII };
  71.    /* Get size of that array. */
  72.    const int arraysSize = sizeof(arrays) / sizeof(char*);
  73.  
  74.    /* atoi(): Does not detect errors! */
  75.    for (idx = 0; idx < arraysSize; ++idx)
  76.    {
  77.       int integer = atoi(arrays[idx]);
  78.  
  79.       printf("%d: atoi with \"%s\" %*s to integer: %+d\n",
  80.              idx,
  81.              arrays[idx],
  82.              8 - strlen (arrays[idx]),
  83.              "",
  84.              integer);
  85.    }
  86.    printf("\n");
  87.  
  88.    /* sscanf(): Error detection by using the matched item count. */
  89.    for (idx = 0; idx < arraysSize; ++idx)
  90.    {
  91.       int integer = 0;
  92.       int itemCount = sscanf(arrays[idx], "%d", &integer);
  93.  
  94.       printf("%d: sscanf with \"%s\" %*s to integer: %+d | itemCount = %d",
  95.              idx,
  96.              arrays[idx],
  97.              8 - strlen (arrays[idx]),
  98.              "",
  99.              integer,
  100.              itemCount);
  101.  
  102.       if (0 == itemCount)
  103.       {
  104.          printf(" --> Error!");
  105.       }
  106.       printf("\n");
  107.    }
  108.    printf("\n");
  109.  
  110.    /* strtol(): Error detection by using errno and returned end pointer. */
  111.    for (idx = 0; idx < arraysSize; ++idx)
  112.    {
  113.       char*     endPtr  = NULL;
  114.       ptrdiff_t ptrDiff = 0;
  115.       errno             = 0;
  116.       /* You have to check if the long can be stored in the int, not done here! */
  117.       int integer = (int) strtol(arrays[idx], &endPtr, 10);
  118.       ptrDiff = endPtr - arrays[idx];
  119.  
  120.       printf("%d: strtol with \"%s\" %*s to integer: %+d | errno =  %d, StartPtr = %p, EndPtr = %p, PtrDiff = %ld",
  121.              idx,
  122.              arrays[idx],
  123.              8 - strlen (arrays[idx]),
  124.              "",
  125.              integer,
  126.              errno,
  127.              (void*) arrays[idx],
  128.              (void*) endPtr,
  129.              ptrDiff);
  130.  
  131.       if (0 != errno || 0 == ptrDiff)
  132.       {
  133.          printf(" --> Error!");
  134.       }
  135.       printf("\n");
  136.    }
  137.    printf("\n");
  138.  
  139.    /* my_strtol: Same as strtol here. */
  140.    for (idx = 0; idx < arraysSize; ++idx)
  141.    {
  142.       char*     endPtr  = NULL;
  143.       ptrdiff_t ptrDiff = 0;
  144.       errno             = 0;
  145.       /* You have to check if the long can be stored in the int, not done here! */
  146.       int integer = (int) my_strtol(arrays[idx], &endPtr, 10);
  147.       ptrDiff = endPtr - arrays[idx];
  148.  
  149.       printf("%d: my_strtol with \"%s\" %*s to integer: %+d | errno =  %d, StartPtr = %p, EndPtr = %p, PtrDiff = %ld",
  150.              idx,
  151.              arrays[idx],
  152.              8 - strlen (arrays[idx]),
  153.              "",
  154.              integer,
  155.              errno,
  156.              (void*) arrays[idx],
  157.              (void*) endPtr,
  158.              ptrDiff);
  159.  
  160.       if (0 != errno || 0 == ptrDiff)
  161.       {
  162.          printf(" --> Error!");
  163.       }
  164.       printf("\n");
  165.    }
  166.  
  167.    return 0;
  168. }
Success #stdin #stdout 0s 9432KB
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stdin
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Standard input is empty
stdout
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0: atoi with "3"         to integer: +3
1: atoi with "    3   "  to integer: +3
2: atoi with "   -3   "  to integer: -3
3: atoi with "str 3   "  to integer: +0
4: atoi with "str-3   "  to integer: +0
5: atoi with "    3str"  to integer: +3
6: atoi with "   -3str"  to integer: -3
7: atoi with "str-3str"  to integer: +0
8: atoi with "s-r-3str"  to integer: +0

0: sscanf with "3"         to integer: +3 | itemCount = 1
1: sscanf with "    3   "  to integer: +3 | itemCount = 1
2: sscanf with "   -3   "  to integer: -3 | itemCount = 1
3: sscanf with "str 3   "  to integer: +0 | itemCount = 0 --> Error!
4: sscanf with "str-3   "  to integer: +0 | itemCount = 0 --> Error!
5: sscanf with "    3str"  to integer: +3 | itemCount = 1
6: sscanf with "   -3str"  to integer: -3 | itemCount = 1
7: sscanf with "str-3str"  to integer: +0 | itemCount = 0 --> Error!
8: sscanf with "s-r-3str"  to integer: +0 | itemCount = 0 --> Error!

0: strtol with "3"         to integer: +3 | errno =  0, StartPtr = 0x7ffc321c01b0, EndPtr = 0x7ffc321c01b1, PtrDiff = 1
1: strtol with "    3   "  to integer: +3 | errno =  0, StartPtr = 0x7ffc321c01c0, EndPtr = 0x7ffc321c01c5, PtrDiff = 5
2: strtol with "   -3   "  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c01d0, EndPtr = 0x7ffc321c01d5, PtrDiff = 5
3: strtol with "str 3   "  to integer: +0 | errno =  0, StartPtr = 0x7ffc321c01e0, EndPtr = 0x7ffc321c01e0, PtrDiff = 0 --> Error!
4: strtol with "str-3   "  to integer: +0 | errno =  0, StartPtr = 0x7ffc321c01f0, EndPtr = 0x7ffc321c01f0, PtrDiff = 0 --> Error!
5: strtol with "    3str"  to integer: +3 | errno =  0, StartPtr = 0x7ffc321c0200, EndPtr = 0x7ffc321c0205, PtrDiff = 5
6: strtol with "   -3str"  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c0210, EndPtr = 0x7ffc321c0215, PtrDiff = 5
7: strtol with "str-3str"  to integer: +0 | errno =  0, StartPtr = 0x7ffc321c0220, EndPtr = 0x7ffc321c0220, PtrDiff = 0 --> Error!
8: strtol with "s-r-3str"  to integer: +0 | errno =  0, StartPtr = 0x7ffc321c0230, EndPtr = 0x7ffc321c0230, PtrDiff = 0 --> Error!

0: my_strtol with "3"         to integer: +3 | errno =  0, StartPtr = 0x7ffc321c01b0, EndPtr = 0x7ffc321c01b1, PtrDiff = 1
1: my_strtol with "    3   "  to integer: +3 | errno =  0, StartPtr = 0x7ffc321c01c0, EndPtr = 0x7ffc321c01c5, PtrDiff = 5
2: my_strtol with "   -3   "  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c01d0, EndPtr = 0x7ffc321c01d5, PtrDiff = 5
3: my_strtol with "str 3   "  to integer: +3 | errno =  0, StartPtr = 0x7ffc321c01e0, EndPtr = 0x7ffc321c01e5, PtrDiff = 5
4: my_strtol with "str-3   "  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c01f0, EndPtr = 0x7ffc321c01f5, PtrDiff = 5
5: my_strtol with "    3str"  to integer: +3 | errno =  0, StartPtr = 0x7ffc321c0200, EndPtr = 0x7ffc321c0205, PtrDiff = 5
6: my_strtol with "   -3str"  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c0210, EndPtr = 0x7ffc321c0215, PtrDiff = 5
7: my_strtol with "str-3str"  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c0220, EndPtr = 0x7ffc321c0225, PtrDiff = 5
8: my_strtol with "s-r-3str"  to integer: -3 | errno =  0, StartPtr = 0x7ffc321c0230, EndPtr = 0x7ffc321c0235, PtrDiff = 5
https://ideone.com/jq5K05
language:
C (gcc 8.3)
created:
6 years ago
visibility:
public

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