1  #include <stdio.h>
 2  #include <stdlib.h>
 3  #include <string.h>
 4  #include <stdint.h>
 5  
 6  struct initrd_header {
 7      uint32_t nfiles;
 8  };
 9  
10  struct initrd_file_header {
11      uint8_t magic;
12      char name[64];
13      uint32_t offset;
14      uint32_t length;
15  };
16  
17  int main(int argc, char** argv) {
18      if (argc < 3) {
19          printf("Usage: %s <output.img> <file1> [file2] ...\n", argv[0]);
20          return 1;
21      }
22      
23      int nfiles = argc - 2;
24      struct initrd_header headers;
25      headers.nfiles = nfiles;
26      
27      FILE* output = fopen(argv[1], "wb");
28      if (!output) {
29          printf("Error: Cannot create output file\n");
30          return 1;
31      }
32      
33      // Write header
34      fwrite(&headers, sizeof(struct initrd_header), 1, output);
35      
36      // Calculate offsets and write file headers
37      uint32_t offset = sizeof(struct initrd_header) + nfiles * sizeof(struct initrd_file_header);
38      
39      for (int i = 0; i < nfiles; i++) {
40          struct initrd_file_header header;
41          memset(&header, 0, sizeof(header));
42          
43          header.magic = 0xBF;
44          
45          // Extract just the filename (not the full path)
46          char* filename = argv[i + 2];
47          char* slash = strrchr(filename, '/');
48          if (slash) {
49              filename = slash + 1;
50          }
51          
52          strncpy(header.name, filename, 63);
53          header.name[63] = 0;
54          
55          // Get file size
56          FILE* file = fopen(argv[i + 2], "rb");
57          if (!file) {
58              printf("Error: Cannot open %s\n", argv[i + 2]);
59              fclose(output);
60              return 1;
61          }
62          
63          fseek(file, 0, SEEK_END);
64          header.length = ftell(file);
65          fclose(file);
66          
67          header.offset = offset;
68          offset += header.length;
69          
70          fwrite(&header, sizeof(struct initrd_file_header), 1, output);
71      }
72      
73      // Write file data
74      for (int i = 0; i < nfiles; i++) {
75          FILE* file = fopen(argv[i + 2], "rb");
76          if (!file) {
77              printf("Error: Cannot open %s\n", argv[i + 2]);
78              fclose(output);
79              return 1;
80          }
81          
82          char buffer[1024];
83          size_t bytes;
84          while ((bytes = fread(buffer, 1, sizeof(buffer), file)) > 0) {
85              fwrite(buffer, 1, bytes, output);
86          }
87          
88          fclose(file);
89      }
90      
91      fclose(output);
92      printf("Created initrd with %d files\n", nfiles);
93      
94      return 0;
95  }