annotate objgrep/lowlevel.c @ 377:34490934ff02

compal/audio/reg-read-guide written
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 09 Oct 2021 20:24:03 +0000
parents c25367bb7656
children
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1 /*
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2 * This C module implements the low-level steps of file mapping and access.
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3 */
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4
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5 #include <sys/types.h>
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6 #include <sys/file.h>
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7 #include <sys/stat.h>
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8 #include <sys/mman.h>
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9 #include <stdio.h>
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10 #include <stdlib.h>
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11 #include <unistd.h>
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12 #include "globals.h"
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13
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14 mmap_objfile()
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15 {
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16 int fd;
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17 struct stat st;
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18
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19 fd = open(objfilename, O_RDONLY);
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20 if (fd < 0) {
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21 perror(objfilename);
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22 exit(2);
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23 }
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24 fstat(fd, &st);
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25 if (!S_ISREG(st.st_mode)) {
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26 fprintf(stderr, "error: %s is not a regular file\n",
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27 objfilename);
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28 exit(2);
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29 }
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30 objfile_tot_size = st.st_size;
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31 objfilemap = mmap(NULL, objfile_tot_size, PROT_READ, MAP_PRIVATE,
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32 fd, 0L);
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33 if (objfilemap == MAP_FAILED) {
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34 perror("mmap");
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35 exit(2);
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36 }
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37 close(fd);
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38 }
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39
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40 mmap_binfile()
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41 {
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42 int fd;
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43 struct stat st;
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44
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45 fd = open(binfilename, O_RDONLY);
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46 if (fd < 0) {
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47 perror(binfilename);
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48 exit(2);
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49 }
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50 fstat(fd, &st);
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51 if (!S_ISREG(st.st_mode)) {
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52 fprintf(stderr, "error: %s is not a regular file\n",
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53 binfilename);
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54 exit(2);
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55 }
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56 binfile_tot_size = st.st_size;
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57 binfilemap = mmap(NULL, binfile_tot_size, PROT_READ, MAP_PRIVATE,
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58 fd, 0L);
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59 if (binfilemap == MAP_FAILED) {
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60 perror("mmap");
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61 exit(2);
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62 }
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63 close(fd);
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64 }
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65
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66 unsigned
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67 get_u16(ptr)
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68 u_char *ptr;
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69 {
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70 return ptr[0] | ptr[1] << 8;
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71 }
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73 get_s16(ptr)
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74 u_char *ptr;
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75 {
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76 int i;
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78 i = ptr[0] | ptr[1] << 8;
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79 if (i >= 32768)
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80 i -= 65536;
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81 return(i);
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82 }
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83
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84 unsigned
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85 get_u32(ptr)
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86 u_char *ptr;
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87 {
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88 return ptr[0] | ptr[1] << 8 | ptr[2] << 16 | ptr[3] << 24;
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89 }