Map.c

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// Implementation of the Map ADT

// !!! DO NOT MODIFY THIS FILE !!!

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

#include "Map.h"

#define DEFAULT_CAPACITY 8

struct map {
    int size;
    int capacity;
    struct item *items;
};

struct item {
    char *key;
    int value;
};

static int ceilingIndex(Map m, char *key);
static void increaseCapacity(Map m);

Map MapNew(void) {
    Map m = malloc(sizeof(*m));
    if (m == NULL) {
        fprintf(stderr, "Insufficient memory!\n");
        exit(EXIT_FAILURE);
    }

    m->size = 0;
    m->capacity = DEFAULT_CAPACITY;
    m->items = malloc(m->capacity * sizeof(struct item));
    if (m->items == NULL) {
        fprintf(stderr, "error: out of memory\n");
        exit(EXIT_FAILURE);
    }

    return m;
}

void MapFree(Map m) {
    for (int i = 0; i < m->size; i++) {
        free(m->items[i].key);
    }
    free(m->items);
    free(m);
}

void MapSet(Map m, char *key, int value) {
    int index = ceilingIndex(m, key);

    if (index != -1 && strcmp(m->items[index].key, key) == 0) {
        m->items[index].value = value;
        return;
    }

    if (m->size == m->capacity) {
        increaseCapacity(m);
    }

    int insertIndex = index == -1 ? m->size : index;
    for (int i = m->size - 1; i >= insertIndex; i--) {
        m->items[i + 1] = m->items[i];
    }

    m->items[insertIndex] = (struct item){strdup(key), value};
    
    m->size++;
}

// Returns the index of the smallest key that is greater than or equal
// to the given key, or -1 if no such key exists
static int ceilingIndex(Map m, char *key) {
    int index = -1;
    int lo = 0;
    int hi = m->size - 1;

    while (lo <= hi) {
        int mid = (lo + hi) / 2;
        int cmp = strcmp(key, m->items[mid].key);

        if (cmp < 0) {
            index = mid;
            hi = mid - 1;
        } else if (cmp > 0) {
            lo = mid + 1;
        } else {
            return mid;
        }
    }

    return index;
}

static void increaseCapacity(Map m) {
    m->capacity *= 2;
    m->items = realloc(m->items, m->capacity * sizeof(struct item));
    if (m->items == NULL) {
        fprintf(stderr, "error: out of memory\n");
        exit(EXIT_FAILURE);
    }
}

bool MapContains(Map m, char *key) {
    int index = ceilingIndex(m, key);

    return index != -1 && strcmp(m->items[index].key, key) == 0;
}

int MapGet(Map m, char *key) {
    int index = ceilingIndex(m, key);

    if (index == -1 || strcmp(m->items[index].key, key) != 0) {
        fprintf(stderr, "error: key '%s' does not exist\n", key);
        exit(EXIT_FAILURE);
    }

    return m->items[index].value;
}