diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/less-177/os.c

   1 /*
   2  * Operating system dependent routines.
   3  *
   4  * Most of the stuff in here is based on Unix, but an attempt
   5  * has been made to make things work on other operating systems.
   6  * This will sometimes result in a loss of functionality, unless
   7  * someone rewrites code specifically for the new operating system.
   8  *
   9  * The makefile provides defines to decide whether various
  10  * Unix features are present.
  11  */
  12
  13 #include <stdio.h>
  14 #include <signal.h>
  15 #include <setjmp.h>
  16 #include "less.h"
  17
  18 /*
  19  * BSD setjmp() saves (and longjmp() restores) the signal mask.
  20  * This costs a system call or two per setjmp(), so if possible we clear the
  21  * signal mask with sigsetmask(), and use _setjmp()/_longjmp() instead.
  22  * On other systems, setjmp() doesn't affect the signal mask and so
  23  * _setjmp() does not exist; we just use setjmp().
  24  */
  25 #if HAS__SETJMP && SIGSETMASK
  26 #define SET_JUMP        _setjmp
  27 #define LONG_JUMP       _longjmp
  28 #else
  29 #define SET_JUMP        setjmp
  30 #define LONG_JUMP       longjmp
  31 #endif
  32
  33 extern char *getenv();
  34
  35 public int reading;
  36
  37 static jmp_buf read_label;
  38
  39 /*
  40  * Like read() system call, but is deliberately interruptible.
  41  * A call to intread() from a signal handler will interrupt
  42  * any pending iread().
  43  */
  44         public int
  45 iread(fd, buf, len)
  46         int fd;
  47         char *buf;
  48         unsigned int len;
  49 {
  50         register int n;
  51
  52         if (SET_JUMP(read_label))
  53         {
  54                 /*
  55                  * We jumped here from intread.
  56                  */
  57                 reading = 0;
  58 #if SIGSETMASK
  59                 sigsetmask(0);
  60 #endif
  61                 return (READ_INTR);
  62         }
  63
  64         flush();
  65         reading = 1;
  66         n = read(fd, buf, len);
  67         reading = 0;
  68         if (n < 0)
  69                 return (-1);
  70         return (n);
  71 }
  72
  73 /*
  74  * Interrupt a pending iread().
  75  */
  76         public void
  77 intread()
  78 {
  79         LONG_JUMP(read_label, 1);
  80 }
  81
  82 #if GET_TIME
  83         public long
  84 get_time()
  85 {
  86         long t;
  87
  88         time(&t);
  89         return (t);
  90 }
  91 #endif
  92
  93 /*
  94  * errno_message: Return an error message based on the value of "errno".
  95  */
  96
  97 #if PERROR
  98
  99 extern char *sys_errlist[];
 100 extern int sys_nerr;
 101 extern int errno;
 102
 103         public char *
 104 errno_message(filename)
 105         char *filename;
 106 {
 107         register char *p;
 108         register char *m;
 109         char msg[16];
 110
 111         if (errno < sys_nerr)
 112                 p = sys_errlist[errno];
 113         else
 114         {
 115                 sprintf(msg, "Error %d", errno);
 116                 p = msg;
 117         }
 118         m = (char *) ecalloc(strlen(filename) + strlen(p) + 3, sizeof(char));
 119         sprintf(m, "%s: %s", filename, p);
 120         return (m);
 121 }
 122
 123 #else
 124
 125         public char *
 126 errno_message(filename)
 127         char *filename;
 128 {
 129         register char *m;
 130         static char msg[] = ": cannot open";
 131
 132         m = (char *) ecalloc(strlen(filename) + sizeof(msg), sizeof(char));
 133         strcpy(m, filename);
 134         strcat(m, msg);
 135         return (m);
 136 }
 137
 138 #endif