63 lines
1.2 KiB
C
63 lines
1.2 KiB
C
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// Implementation of cprintf console output for user environments,
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// based on printfmt() and the sys_cputs() system call.
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//
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// cprintf is a debugging statement, not a generic output statement.
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// It is very important that it always go to the console, especially when
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// debugging file descriptor code!
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#include <inc/types.h>
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#include <inc/stdio.h>
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#include <inc/stdarg.h>
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#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 idx; // current buffer index
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int cnt; // total bytes printed so far
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char buf[256];
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};
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static void
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putch(int ch, struct printbuf *b)
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{
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b->buf[b->idx++] = ch;
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if (b->idx == 256-1) {
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sys_cputs(b->buf, b->idx);
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b->idx = 0;
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}
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b->cnt++;
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}
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int
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vcprintf(const char *fmt, va_list ap)
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{
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struct printbuf b;
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b.idx = 0;
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b.cnt = 0;
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vprintfmt((void*)putch, &b, fmt, ap);
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sys_cputs(b.buf, b.idx);
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return b.cnt;
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}
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int
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cprintf(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 = vcprintf(fmt, ap);
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va_end(ap);
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return cnt;
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}
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