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  1. #include <stdio.h>		// for fread, fwrite, fopen, FILE, fclose
  2. #include <stdlib.h>		// for NULL, EXIT_FAILURE.
  3. #include <stddef.h>		// for size_t
  4. #include <stdbool.h>	// for bool.
  5.  
  6. struct unko
  7. {
  8. 	double x;
  9. 	double y;
  10. };
  11.  
  12. typedef struct unko unko;
  13.  
  14. bool file_writer(char const *filename, unko const data[static 1], size_t element_count)
  15. {
  16. 	FILE *fo;
  17. 	if ( element_count < 1
  18. 		|| (fo = fopen(filename, "wb")) == NULL
  19. 		|| fwrite(&element_count, sizeof element_count, 1, fo) != 1
  20. 		|| fwrite(data, sizeof(unko), element_count, fo) != element_count )
  21. 	{
  22. 		return false;
  23. 	}
  24.  
  25. 	fclose(fo);
  26. 	return true;
  27. }
  28.  
  29. // データレイアウト
  30. // [0] 要素数。整数。
  31. // :
  32. // [7]
  33. // 
  34. // [7 + 0] 1番目のxの開始
  35. // :
  36. // [7 + 8] 1番目のyの開始
  37. // 
  38. // [7 + i * 16 + 0] i+1番目のxの開始
  39. // :
  40. // [7 + i * 16 + 7] i+1番目のxの終了
  41. // [7 + i * 16 + 8] i+1番目のyの開始
  42. // :
  43. // [7 + i * 16 + 15] i+1番目のyの終了
  44. bool file_reader(char const *filename, unko data[], size_t data_size, size_t *p_read_count)
  45. {
  46. 	size_t element_count;
  47. 	FILE *fi = fopen(filename, "rb");
  48. 	if ( fi == NULL
  49. 		|| fread(&element_count, sizeof element_count, 1, fi) != 1
  50. 		|| element_count > data_size
  51. 		|| fread(data, sizeof(unko), element_count, fi) != element_count )
  52. 	{
  53. 		fclose(fi);
  54. 		return false;
  55. 	}
  56.  
  57. 	fclose(fi);
  58. 	*p_read_count = element_count;
  59. 	return true;
  60. }
  61.  
  62. int main()
  63. {
  64. 	char const *filename = "unko.dat";
  65.  
  66. 	{
  67. 		unko test_data[] = { { .x = 1.234, .y = 2.345 }, { .x = 0.001, .y = -0.987 }, { .x = 3.14, .y = 2.718 } };
  68. 		if ( !file_writer(filename, test_data, sizeof test_data / sizeof *test_data) )
  69. 		{
  70. 			printf("oops..\n");
  71. 			return EXIT_FAILURE;
  72. 		}
  73. 	}
  74.  
  75. 	{
  76. 		unko test_data2[100];
  77. 		size_t element_count;
  78. 		if ( !file_reader(filename, test_data2, sizeof test_data2 / sizeof *test_data2, &element_count) )
  79. 		{
  80. 			printf("oops..\n");
  81. 			return EXIT_FAILURE;
  82. 		}
  83.  
  84. 		printf("unko count = %zu\n", element_count);
  85.  
  86. 		for ( int i = 0; i < (int)element_count; i++ )
  87. 			printf("unko #%d: x=%.3f, y=%.3f\n", i, test_data2[i].x, test_data2[i].y);
  88. 	}
  89. }
  90.  
Runtime error #stdin #stdout 0s 2424KB
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stdin
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Standard input is empty
stdout
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oops..
https://ideone.com/O2o255
language:
C99 (gcc 8.3)
created:
10 years ago
visibility:
secret

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