nc_string.c

/*
 * twemproxy - A fast and lightweight proxy for memcached protocol.
 * Copyright (C) 2011 Twitter, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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

#include <nc_core.h>

/*
 * String (struct string) is a sequence of unsigned char objects terminated
 * by the null character '\0'. The length of the string is pre-computed and
 * made available explicitly as an additional field. This means that we don't
 * have to walk the entire character sequence until the null terminating
 * character everytime that the length of the String is requested
 *
 * The only way to create a String is to initialize it using, string_init()
 * and duplicate an existing String - string_duplicate() or copy an existing
 * raw sequence of character bytes - string_copy(). Such String's must be
 * freed using string_deinit()
 *
 * We can also create String as reference to raw string - string_set_raw()
 * or to text string - string_set_text() or string(). Such String don't have
 * to be freed.
 */

void
string_init(struct string *str)
{
    str->len = 0;
    str->data = NULL;
}

void
string_deinit(struct string *str)
{
    ASSERT((str->len == 0 && str->data == NULL) ||
           (str->len != 0 && str->data != NULL));

    if (str->data != NULL) {
        nc_free(str->data);
        string_init(str);
    }
}

bool
string_empty(const struct string *str)
{
    ASSERT((str->len == 0 && str->data == NULL) ||
           (str->len != 0 && str->data != NULL));
    return str->len == 0 ? true : false;
}

rstatus_t
string_duplicate(struct string *dst, const struct string *src)
{
    ASSERT(dst->len == 0 && dst->data == NULL);
    ASSERT(src->len != 0 && src->data != NULL);

    dst->data = nc_strndup(src->data, src->len + 1);
    if (dst->data == NULL) {
        return NC_ENOMEM;
    }

    dst->len = src->len;
    dst->data[dst->len] = '\0';

    return NC_OK;
}

rstatus_t
string_copy(struct string *dst, const uint8_t *src, uint32_t srclen)
{
    ASSERT(dst->len == 0 && dst->data == NULL);
    ASSERT(src != NULL && srclen != 0);

    dst->data = nc_strndup(src, srclen + 1);
    if (dst->data == NULL) {
        return NC_ENOMEM;
    }

    dst->len = srclen;
    dst->data[dst->len] = '\0';

    return NC_OK;
}

int
string_compare(const struct string *s1, const struct string *s2)
{
    if (s1->len != s2->len) {
        return s1->len > s2->len ? 1 : -1;
    }

    return nc_strncmp(s1->data, s2->data, s1->len);
}

static char *
_safe_utoa(int _base, uint64_t val, char *buf)
{
    char hex[] = "0123456789abcdef";
    uint32_t base = (uint32_t) _base;
    *buf-- = 0;
    do {
        *buf-- = hex[val % base];
    } while ((val /= base) != 0);
    return buf + 1;
}

static char *
_safe_itoa(int base, int64_t val, char *buf)
{
    char hex[] = "0123456789abcdef";
    char *orig_buf = buf;
    const int32_t is_neg = (val < 0);
    *buf-- = 0;

    if (is_neg) {
        val = -val;
    }
    if (is_neg && base == 16) {
        int ix;
        val -= 1;
        for (ix = 0; ix < 16; ++ix)
            buf[-ix] = '0';
    }

    do {
        *buf-- = hex[val % base];
    } while ((val /= base) != 0);

    if (is_neg && base == 10) {
        *buf-- = '-';
    }

    if (is_neg && base == 16) {
        int ix;
        buf = orig_buf - 1;
        for (ix = 0; ix < 16; ++ix, --buf) {
            /* *INDENT-OFF* */
            switch (*buf) {
            case '0': *buf = 'f'; break;
            case '1': *buf = 'e'; break;
            case '2': *buf = 'd'; break;
            case '3': *buf = 'c'; break;
            case '4': *buf = 'b'; break;
            case '5': *buf = 'a'; break;
            case '6': *buf = '9'; break;
            case '7': *buf = '8'; break;
            case '8': *buf = '7'; break;
            case '9': *buf = '6'; break;
            case 'a': *buf = '5'; break;
            case 'b': *buf = '4'; break;
            case 'c': *buf = '3'; break;
            case 'd': *buf = '2'; break;
            case 'e': *buf = '1'; break;
            case 'f': *buf = '0'; break;
            }
            /* *INDENT-ON* */
        }
    }
    return buf + 1;
}

static const char *
_safe_check_longlong(const char *fmt, int32_t * have_longlong)
{
    *have_longlong = false;
    if (*fmt == 'l') {
        fmt++;
        if (*fmt != 'l') {
            *have_longlong = (sizeof(long) == sizeof(int64_t));
        } else {
            fmt++;
            *have_longlong = true;
        }
    }
    return fmt;
}

int
_safe_vsnprintf(char *to, size_t size, const char *format, va_list ap)
{
    char *start = to;
    char *end = start + size - 1;
    for (; *format; ++format) {
        int32_t have_longlong = false;
        if (*format != '%') {
            if (to == end) {    /* end of buffer */
                break;
            }
            *to++ = *format;    /* copy ordinary char */
            continue;
        }
        ++format;               /* skip '%' */

        format = _safe_check_longlong(format, &have_longlong);

        switch (*format) {
        case 'd':
        case 'i':
        case 'u':
        case 'x':
        case 'p':
            {
                int64_t ival = 0;
                uint64_t uval = 0;
                if (*format == 'p')
                    have_longlong = (sizeof(void *) == sizeof(uint64_t));
                if (have_longlong) {
                    if (*format == 'u') {
                        uval = va_arg(ap, uint64_t);
                    } else {
                        ival = va_arg(ap, int64_t);
                    }
                } else {
                    if (*format == 'u') {
                        uval = va_arg(ap, uint32_t);
                    } else {
                        ival = va_arg(ap, int32_t);
                    }
                }

                {
                    char buff[22];
                    const int base = (*format == 'x' || *format == 'p') ? 16 : 10;

		            /* *INDENT-OFF* */
                    char *val_as_str = (*format == 'u') ?
                        _safe_utoa(base, uval, &buff[sizeof(buff) - 1]) :
                        _safe_itoa(base, ival, &buff[sizeof(buff) - 1]);
		            /* *INDENT-ON* */

                    /* Strip off "ffffffff" if we have 'x' format without 'll' */
                    if (*format == 'x' && !have_longlong && ival < 0) {
                        val_as_str += 8;
                    }

                    while (*val_as_str && to < end) {
                        *to++ = *val_as_str++;
                    }
                    continue;
                }
            }
        case 's':
            {
                const char *val = va_arg(ap, char *);
                if (!val) {
                    val = "(null)";
                }
                while (*val && to < end) {
                    *to++ = *val++;
                }
                continue;
            }
        }
    }
    *to = 0;
    return (int)(to - start);
}

int
_safe_snprintf(char *to, size_t n, const char *fmt, ...)
{
    int result;
    va_list args;
    va_start(args, fmt);
    result = _safe_vsnprintf(to, n, fmt, args);
    va_end(args);
    return result;
}