putbackdog.c

早期freebsd实现

// Test streambuf::sputbackc

#include <iostream.h>
#include <stdlib.h>
#include <string.h>

// Read either "dog", "hound", or "hounddog".
// If "dog" is found, return 1.
// If "hound" is found, return 2.
// If "hounddog" is found, return 3.
// If non of these are found, return -1.

void unget_string(streambuf *sb, char *str, int count)
{
    for (str += count; -- count >= 0; )
	sb->sputbackc(*--str);
}

int my_scan(streambuf* sb)
{
    char buffer[20];
    // Try reading "hounddog":
    int count;
    count = sb->sgetn(buffer, 8);
    if (count == 8 && strncmp(buffer, "hounddog", 8) == 0)
      return 3;
    // No, no "hounddog":  Backup to 'fence' ...
    unget_string(sb, buffer, count);
    // ... and try reading "dog":
    count = sb->sgetn(buffer, 3);
    if (count == 3 && strncmp(buffer, "dog", 3) == 0)
      return 1;
    // No, no "dog" either:  Backup to 'fence' ...
    unget_string(sb, buffer, count);
    // ... and try reading "hound":
    count = sb->sgetn(buffer, 5);
    if (count == 5 && strncmp(buffer, "hound", 5) == 0)
      return 2;
    // No, no "hound" either:  Backup to 'fence' and signal failure.
    unget_string(sb, buffer, count);
    return -1;
}

int main(int argc, char **argv)
{
    streambuf *sb = cin.rdbuf();
    if (argc > 1 && strncmp(argv[1], "-b", 2) == 0) {
	streambuf *ret;
	int buffer_size = atoi(&argv[1][2]);
	if (buffer_size == 0)
	    ret = sb->setbuf(NULL, 0);
	else
	    ret = sb->setbuf(new char[buffer_size], buffer_size);
	if (ret != sb)
	    cerr << "Warning: cin.rdbuf()->setbuf failed!\n";
    }
    for (;;) {
	int code = my_scan(sb);
	int ch = sb->sbumpc();
	if (code == -1 && ch == EOF)
	    break;
	int n = 0;
	while (ch != EOF && ch != '\n') {
	    n++;
	    ch = sb->sbumpc();
	};
	if (ch == EOF) {
	    cout << "[Unexpected EOF]\n";
	    break;
	}
	cout << "Code: " << code << " followed by " << n << " chars\n";
    }
}