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  1. /**
  2.  * This script implements a very simple string copy that is the same length
  3.  * or less bytes. The copied string only contains printable characters.
  4.  */
  5.  
  6. #include <assert.h>
  7. #include <stdio.h>
  8. #include <stdlib.h>
  9. #include <string.h>
  10. #include <stdbool.h>
  11.  
  12. // Duplicate the string src without any non-printable characters.
  13. char* strcpy_pc(const char* src)
  14. {
  15.     assert(src != NULL);
  16.  
  17.     char* dst        = NULL;
  18.     int   src_offset = 0;
  19.     int   dst_offset = 0;
  20.  
  21.     // To clean the string, we'll first allocate all the required memory:
  22.     dst = malloc(sizeof(char) * strlen(src) + 1);
  23.     assert(dst != NULL);
  24.  
  25.     // Next, loop over each character and if it's permitted, add it:
  26.     while (true)
  27.     {
  28.         // If we run over a null byte - copy it and exit.
  29.         if (src[src_offset] == 0)
  30.         {
  31.             dst[dst_offset] = 0;
  32.  
  33.             // We can now resize to the memory that's needed.
  34.             dst = realloc(dst, sizeof(char) * (strlen(dst) + 1));
  35.             assert(dst != NULL);
  36.  
  37.             return dst;
  38.         }
  39.  
  40.         // Skip DEL byte (0x7F) and anything below 31 (0x1F).
  41.         if (src[src_offset] < 32 || src[src_offset] == 127)
  42.         {
  43.             src_offset++;
  44.             continue;
  45.         }
  46.  
  47.         // For all remaining bytes, copy them.
  48.         dst[dst_offset] = src[src_offset];
  49.         dst_offset++;
  50.         src_offset++;
  51.     }
  52. }
  53.  
  54. //
  55. // Tests
  56. //
  57.  
  58. #include "../picotest/lib/framework.h"
  59.  
  60. IT_SHOULD(do_nothing_with_an_empty_string, {
  61.     char* dst = strcpy_pc("");
  62.  
  63.     ASSERT_STR_EQ("", dst);
  64. })
  65.  
  66. IT_SHOULD(return_identical_string_with_no_printable_characters, {
  67.     char* src = "hello";
  68.     char* dst = strcpy_pc(src);
  69.  
  70.     ASSERT_STR_EQ(src, dst);
  71. })
  72.  
  73. IT_SHOULD(remove_non_printable_characters_at_the_end, {
  74.     char* src = "hello\x01";
  75.     char* dst = strcpy_pc(src);
  76.  
  77.     ASSERT_STR_EQ("hello", dst);
  78. })
  79.  
  80. IT_SHOULD(remove_non_printable_characters_anywhere_in_the_string, {
  81.     char* src = "h\ae\x01llo\x01";
  82.     char* dst = strcpy_pc(src);
  83.  
  84.     ASSERT_STR_EQ("hello", dst);
  85. })
  86.  
  87. int main()
  88. {
  89.     BEGIN_TESTING;
  90.  
  91.     RUN_TEST(do_nothing_with_an_empty_string);
  92.     RUN_TEST(return_identical_string_with_no_printable_characters);
  93.     RUN_TEST(remove_non_printable_characters_at_the_end);
  94.     RUN_TEST(remove_non_printable_characters_anywhere_in_the_string);
  95.  
  96.     CONCLUDE_TESTING;
  97. }
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