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35 lines
837 B
C
35 lines
837 B
C
#include <unistd.h>
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#include "buffer.h"
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ssize_t buffer_seek(buffer* b,size_t len) {
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size_t leftinbuf = b->n - b->p;
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ssize_t r;
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if ((ssize_t)len < 0) return -1; // can't signal back how much we read, so error out
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r = (ssize_t)len;
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if (len <= leftinbuf) {
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b->p += len;
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return len;
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} else {
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// want to skip more than there was in the buffer
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len -= leftinbuf;
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b->p = 0; // clear buffer
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b->n = 0;
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/* change position in underlying file */
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if (b->fd != -1 &&
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lseek(b->fd, len, SEEK_CUR) != -1) return len;
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// either we have no fd or input is not seekable
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// call read repeatedly
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while (len > 0) {
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ssize_t r = buffer_feed(b);
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if (r < 0) return -1;
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if ((size_t)r > len) r = len; // can't happen
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len -= r;
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b->p = b->n = 0;
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}
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return r;
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}
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}
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