Added final simulation time to output, added locale - breaks ANSI;

xtc-length.c

 #include <stdio.h>
 #include <inttypes.h>
+#include <locale.h>
+#include <string.h>
 
 /*
  * Program for finding the number of frames and atoms in a GROMACS XTC file.
@@ -11,7 +13,14 @@ uint32_t u4_from_buffer(const uint8_t *b){
     return b[0] << 24 | b[1] << 16 | b[2] << 8 | b[3] << 0;
 }
 
-int get_xtc_num_frames(const char *filename, int *nframes, int *natoms){
+void print_header(const uint8_t header[92]){
+    printf("%4d", u4_from_buffer(header+0));
+    printf("%8d", u4_from_buffer(header+4));
+    printf("%12d", u4_from_buffer(header+8));
+    printf("\n");
+}
+
+int get_xtc_num_frames(const char *filename, int *nframes, int *natoms, float *psec){
     FILE *xtc = fopen(filename, "rb");
     if(!xtc) return -1;
 
@@ -19,29 +28,35 @@ int get_xtc_num_frames(const char *filename, int *nframes, int *natoms){
 
     *nframes = 0;
     while(fread(header, 92, 1, xtc)){                       // Loop over frames
+        //print_header(header);
         (*nframes)++;
         *natoms = u4_from_buffer(header+4);
         uint32_t frame_size = u4_from_buffer(header+88);    // Read frame size from header
         uint32_t skip = (frame_size+3) & ~((uint32_t)3);    // Round up to 4 bytes
         fseek(xtc, skip, SEEK_CUR);                         // Skip to next header
     }
+    uint32_t ps_tmp = u4_from_buffer(header+12);
+    memcpy(psec, &ps_tmp, 4);
 
     fclose(xtc);
     return 0;
 }
 
 int main(const int argc, const char *argv[]){
+    setlocale(LC_ALL, "");
+
     if(argc < 2){
         printf("ERROR: Incorrect usage - must give input filename\n");
         return -1;
     }
 
     int nframes, natoms;
-    if(get_xtc_num_frames(argv[1], &nframes, &natoms)){
+    float psec;
+    if(get_xtc_num_frames(argv[1], &nframes, &natoms, &psec)){
         printf("ERROR: Error reading XTC file\n");
         return -1;
     }
 
-    printf("Trajectory contains %d frames of %d atoms.\n", nframes, natoms);
+    printf("Trajectory contains %'d frames (%'.2f ns) of %'d atoms.\n", nframes, psec/1000, natoms);
     return 0;
 }