config.c

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "config.h"

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

#define CONFIG_MAX_ITEMS 128
#define CONFIG_MAX_STRINGDATA (4096 * 3)

static char buffer[CONFIG_MAX_STRINGDATA];
static size_t buffer_next = 0;

typedef struct {
    char *key;
    char *val;
    size_t klen;
    size_t vlen;
} kv_t;

static kv_t entry[CONFIG_MAX_ITEMS];
static size_t entry_count;

size_t config_to_string(char *ptr, size_t max) {
    char *start = ptr;

    if (max == 0) {
        return 0;
    }

    for (size_t n = 0; n < entry_count; n++) {
        if ((entry[n].klen + entry[n].vlen + 3) > max) {
            // require space for: space + key + equal + value + null
            break;
        }
        if (n > 0) {
            *ptr++ = ' ';
            max--;
        }
        memcpy(ptr, entry[n].key, entry[n].klen);
        ptr += entry[n].klen;
        max -= entry[n].klen;
        if (entry[n].vlen) {
            *ptr++ = '=';
            max--;
            memcpy(ptr, entry[n].val, entry[n].vlen);
            ptr += entry[n].vlen;
            max -= entry[n].vlen;
        }
    }
    *ptr++ = 0;
    return ptr - start;
}

static void entry_add(const char *key, size_t klen, const char *val, size_t vlen) {
    if (klen == 0) {
        // empty keys are not allowed
        return;
    }

    if ((klen > 1024) || (vlen > 1024)) {
        // huge keys and values are not allowed
        return;
    }

    if ((sizeof(buffer) - buffer_next) < (klen + vlen + 2)) {
        // give up if it won't fit
        return;
    }

    size_t n;
    for (n = 0; n < entry_count; n++) {
        if ((entry[n].klen == klen) && !memcmp(key, entry[n].key, klen)) {
            goto write_value;
        }
    }
    if (n == CONFIG_MAX_ITEMS) {
        // no space in table
        return;
    }

    // new entry
    entry_count++;
    entry[n].key = buffer + buffer_next;
    entry[n].klen = klen;
    memcpy(entry[n].key, key, klen);
    entry[n].key[klen] = 0;
    buffer_next += klen + 1;

write_value:
    entry[n].val = buffer + buffer_next;
    entry[n].vlen = vlen;
    memcpy(entry[n].val, val, vlen);
    entry[n].val[vlen] = 0;
    buffer_next += vlen + 1;
}

void config_set(const char *key, const char *val) { entry_add(key, strlen(key), val, strlen(val)); }

void config_init(const char *ptr, size_t len) {
    const char *key;
    const char *val;

restart:
    while (len > 0) {
        if (isspace(*ptr)) {
            ptr++;
            len--;
            continue;
        }
        key = ptr;
        while (len > 0) {
            if (*ptr == '=') {
                size_t klen = ptr - key;
                ptr++;
                len--;
                val = ptr;
                while ((len > 0) && !isspace(*ptr)) {
                    len--;
                    ptr++;
                }
                size_t vlen = ptr - val;
                entry_add(key, klen, val, vlen);
                goto restart;
            }
            if (isspace(*ptr)) {
                break;
            }
            ptr++;
            len--;
        }
        size_t klen = ptr - key;
        entry_add(key, klen, NULL, 0);
    }
}

const char *config_get(const char *key, const char *_default) {
    size_t klen = strlen(key);
    for (size_t n = 0; n < entry_count; n++) {
        if ((entry[n].klen == klen) && !memcmp(key, entry[n].key, klen)) {
            return entry[n].val;
        }
    }
    return _default;
}

uint32_t config_get_uint32(const char *key, uint32_t _default) {
    const char *val = config_get(key, NULL);
    if (val == NULL) {
        return _default;
    }
    return atol(val);
}