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vtools_genesis          1 #include <errno.h>
vtools_genesis          2 #include <limits.h>
vtools_genesis          3 #include <signal.h>
vtools_genesis          4 #include <unistd.h>
vtools_genesis          5 #include <stdint.h>
vtools_genesis          6 #include "system.h"
vtools_genesis          7 #include "cmpbuf.h"
vtools_genesis          8 
vtools_genesis          9 /* Read |nbytes| bytes from descriptor |fd| into |buf|.  |nbytes| must
vtools_genesis         10    not be |SIZE_MAX|.  Return the number of characters successfully
vtools_genesis         11    read.  On error, return |SIZE_MAX|, setting |errno|.  The number
vtools_genesis         12    returned is always |nbytes| unless end-of-file or error.  */
vtools_genesis         13 
vtools_genesis         14 size_t
vtools_genesis         15 block_read(int fd, char *buf, size_t nbytes) {
vtools_genesis         16     char *bp = buf;
vtools_genesis         17     char const *buflim = buf + nbytes;
vtools_genesis         18     size_t readlim = MIN (SSIZE_MAX, SIZE_MAX);
vtools_genesis         19 
vtools_genesis         20     do {
vtools_genesis         21         size_t bytes_remaining = buflim - bp;
vtools_genesis         22         size_t bytes_to_read = MIN (bytes_remaining, readlim);
vtools_genesis         23         ssize_t nread = read(fd, bp, bytes_to_read);
vtools_genesis         24         if (nread <= 0) {
vtools_genesis         25             if (nread == 0)
vtools_genesis         26                 break;
vtools_genesis         27             return SIZE_MAX;
vtools_genesis         28         }
vtools_genesis         29         bp += nread;
vtools_genesis         30     } while (bp < buflim);
vtools_genesis         31 
vtools_genesis         32     return bp - buf;
vtools_genesis         33 }
vtools_genesis         34 
vtools_genesis         35 /* Least common multiple of two buffer sizes |a| and |b|.  However, if
vtools_genesis         36    either |a| or |b| is zero, or if the multiple is greater than
vtools_genesis         37    |lcm_max|, return a reasonable buffer size. */
vtools_genesis         38 
vtools_genesis         39 size_t
vtools_genesis         40 buffer_lcm(size_t a, size_t b, size_t lcm_max) {
vtools_genesis         41     size_t lcm, m, n, q, r;
vtools_genesis         42 
vtools_genesis         43     /* Yield reasonable values if buffer sizes are zero.  */
vtools_genesis         44     if (!a)
vtools_genesis         45         return b ? b : 8 * 1024;
vtools_genesis         46     if (!b)
vtools_genesis         47         return a;
vtools_genesis         48 
vtools_genesis         49     /* |n = gcd (a, b)| */
vtools_genesis         50     for (m = a, n = b; (r = m % n) != 0; m = n, n = r)
vtools_genesis         51         continue;
vtools_genesis         52 
vtools_genesis         53     /* Yield a if there is an overflow.  */
vtools_genesis         54     q = a / n;
vtools_genesis         55     lcm = q * b;
vtools_genesis         56     return lcm <= lcm_max && lcm / b == q ? lcm : a;
vtools_genesis         57 }