82 lines
1.4 KiB
C
82 lines
1.4 KiB
C
#include <inc/lib.h>
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// Collect up to 256 characters into a buffer
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// and perform ONE system call to print all of them,
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// in order to make the lines output to the console atomic
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// and prevent interrupts from causing context switches
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// in the middle of a console output line and such.
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struct printbuf {
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int fd; // file descriptor
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int idx; // current buffer index
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ssize_t result; // accumulated results from write
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int error; // first error that occurred
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char buf[256];
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};
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static void
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writebuf(struct printbuf *b)
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{
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if (b->error > 0) {
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ssize_t result = write(b->fd, b->buf, b->idx);
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if (result > 0)
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b->result += result;
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if (result != b->idx) // error, or wrote less than supplied
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b->error = (result < 0 ? result : 0);
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}
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}
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static void
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putch(int ch, void *thunk)
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{
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struct printbuf *b = (struct printbuf *) thunk;
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b->buf[b->idx++] = ch;
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if (b->idx == 256) {
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writebuf(b);
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b->idx = 0;
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}
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}
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int
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vfprintf(int fd, const char *fmt, va_list ap)
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{
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struct printbuf b;
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b.fd = fd;
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b.idx = 0;
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b.result = 0;
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b.error = 1;
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vprintfmt(putch, &b, fmt, ap);
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if (b.idx > 0)
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writebuf(&b);
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return (b.result ? b.result : b.error);
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}
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int
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fprintf(int fd, const char *fmt, ...)
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{
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va_list ap;
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int cnt;
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va_start(ap, fmt);
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cnt = vfprintf(fd, fmt, ap);
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va_end(ap);
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return cnt;
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}
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int
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printf(const char *fmt, ...)
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{
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va_list ap;
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int cnt;
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va_start(ap, fmt);
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cnt = vfprintf(1, fmt, ap);
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va_end(ap);
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return cnt;
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}
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