switch.d

import stdio;
import string;

/******************************************************
 * Support for switch statements switching on strings.
 * Input:
 *	table[]		sorted array of strings generated by compiler
 *	ca		string to look up in table
 * Output:
 *	result		index of match in table[]
 *			-1 if not in table
 */

extern (C):

int _d_switch_string(char[][] table, char[] ca)
    in
    {
	//printf("in _d_switch_string()\n");
	assert(table.length >= 0);
	assert(ca.length >= 0);

	// Make sure table[] is sorted correctly
	int i;

	for (i = 1; i < table.length; i++)
	{
	    int len1 = table[i - 1].length;
	    int len2 = table[i].length;

	    assert(len1 <= len2);
	    if (len1 == len2)
	    {
		int c;

		c = memcmp(table[i - 1], table[i], len1);
		assert(c < 0);	// c==0 means a duplicate
	    }
	}
    }
    out (result)
    {
	int i;
	int c;

	//printf("out _d_switch_string()\n");
	if (result == -1)
	{
	    // Not found
	    for (i = 0; i < table.length; i++)
	    {
		c = memcmp(table[i], ca, ca.length);
		assert(c != 0);
	    }
	}
	else
	{
	    assert(0 <= result && result < table.length);
	    for (i = 0; 1; i++)
	    {
		assert(i < table.length);
		c = memcmp(table[i], ca, ca.length);
		if (c == 0)
		{
		    assert(i == result);
		    break;
		}
	    }
	}
    }
    body
    {
	//printf("body _d_switch_string()\n");
	int low;
	int high;
	int mid;
	int c;
	char[] pca;

	low = 0;
	high = table.length;

    /*
	// Print table
	printf("ca[] = '%s'\n", (char *)ca);
	for (mid = 0; mid < high; mid++)
	{
	    pca = table[mid];
	    printf("table[%d] = %d, '%s'\n", mid, pca.length, (char *)pca);
	}
    */

	// Do binary search
	while (low < high)
	{
	    mid = (low + high) >> 1;
	    pca = table[mid];
	    c = ca.length - pca.length;
	    if (c == 0)
	    {
		c = memcmp(ca, pca, ca.length);
		if (c == 0)
		{   //printf("found %d\n", mid);
		    return mid;
		}
	    }
	    if (c < 0)
	    {
		high = mid;
	    }
	    else
	    {
		low = mid + 1;
	    }
	}
	//printf("not found\n");
	return -1;		// not found
    }