airscan-memstr.c

/* AirScan (a.k.a. eSCL) backend for SANE
 *
 * Copyright (C) 2019 and up by Alexander Pevzner (pzz@apevzner.com)
 * See LICENSE for license terms and conditions
 *
 * Memory allocation and strings
 */

#include "airscan.h"

#include <assert.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

/******************** Memory allocation ********************/

/* While memory block grows, its size is doubled until
 * MEM_CAP_BLOCK is reached, then it grows linearly,
 * reminding a multiple of whole MEM_CAP_BLOCKs
 */
#define MEM_CAP_BLOCK   65536

/* Each memory block allocated from here has the following
 * control record
 */
typedef struct {
    uint32_t len, cap; /* Block length and capacity in bytes */
} mem_head;

/* Check for OOM
 */
#define mem_check_oom(p,must)                   \
    do{                                         \
        if ((p) == NULL && must) {              \
            log_panic(NULL, "Out of memory");   \
            __builtin_unreachable();            \
        }                                       \
    } while(0)

/* Truncate the vector length, preserving previously allocated buffer
 */
void
mem_trunc (void *p)
{
    ((mem_head*) p)[-1].len = 0;
}

/* Free memory, previously obtained from mem_new()/mem_expand()
 */
void
mem_free (void *p)
{
    if (p != NULL) {
        free(((mem_head*) p) - 1);
    }
}

/* Get memory block length, in bytes
 */
size_t
mem_len_bytes (const void *p)
{
    return p ? ((mem_head*) p)[-1].len : 0;
}

/* Get memory block capacity, in bytes
 */
size_t
mem_cap_bytes (const void *p)
{
    return p ? ((mem_head*) p)[-1].cap : 0;
}

/* Compute allocation size, including mem_head header, in bytes
 */
static inline int
mem_alloc_size(size_t len, size_t extra, size_t elsize)
{
    size_t sz = sizeof(mem_head) + elsize * (len + extra);

    if (sz < MEM_CAP_BLOCK) {
        /* Round up to the next power of 2 */
        sz --;
        sz |= sz >> 1;
        sz |= sz >> 2;
        sz |= sz >> 4;
        sz |= sz >> 8;
        sz |= sz >> 16;
        sz ++;
    } else {
        /* Round up to the next block boundary */
        sz += MEM_CAP_BLOCK - 1;
        sz &= ~(MEM_CAP_BLOCK - 1);
    }

    return sz;
}

/* Helper function: allocate new block of memory
 */
void*
__mem_alloc (size_t len, size_t extra, size_t elsize, bool must)
{
    size_t   sz = mem_alloc_size(len, extra, elsize);
    mem_head *h = calloc(sz, 1);

    if (h == NULL) {
        mem_check_oom(h, must);
        return NULL;
    }

    h->len = len * elsize;
    h->cap = sz - (sizeof(mem_head));

    return h + 1;
}

/* Helper function for memory allocation.
 * Allocated or resizes memory block
 */
void*
__mem_resize (void *p, size_t len, size_t extra, size_t elsize, bool must)
{
    size_t   sz;
    mem_head *h;

    /* If `p' is NULL, just call __mem_alloc() */
    if (p == NULL) {
        return __mem_alloc(len, extra, elsize, must);
    }

    /* Reallocate memory, if required */
    h = ((mem_head*) p) - 1;
    sz = mem_alloc_size(len, extra, elsize);

    if (h->cap + sizeof(mem_head) < sz) {
        h = realloc(h, sz);
        if (h == NULL) {
            mem_check_oom(h, must);
            return NULL;
        }
    }

    /* Zero-fill newly added elements */
    len *= elsize;
    if (len > h->len) {
        memset((char*) (h + 1) + h->len, 0, len - h->len);
    }

    /* Update control header and return a block */
    h->len = len;
    h->cap = sz - (sizeof(mem_head));

    return h + 1;
}

/* Helper function for memory allocation.
 * Shrinks memory block
 */
void
__mem_shrink (void *p, size_t len, size_t elsize)
{
    mem_head *h = ((mem_head*) p) - 1;

    len *= elsize;
    log_assert(NULL, len <= h->len);
    h->len = len;
}

/******************** Strings ********************/
/* Create new string as a lowercase copy of existent string
 */
char*
str_dup_tolower (const char *s1)
{
    char   *s = str_dup(s1);
    size_t i;

    for (i = 0; s[i]; i ++) {
        s[i] = safe_tolower(s[i]);
    }

    return s;
}

/* Create new string and print to it
 */
char*
str_printf (const char *format, ...)
{
    va_list ap;
    char    *s;

    va_start(ap, format);
    s = str_append_vprintf(NULL, format, ap);
    va_end(ap);

    return s;
}

/* Create new string and print to it, va_list version
 */
char*
str_vprintf (const char *format, va_list ap)
{
    return str_append_vprintf(NULL, format, ap);
}

/* Append formatted string to string
 *
 * `s' must be previously created by some of str_XXX functions,
 * `s' will be consumed and the new pointer will be returned
 */
char*
str_append_printf (char *s, const char *format, ...)
{
    va_list ap;

    va_start(ap, format);
    s = str_append_vprintf(s, format, ap);
    va_end(ap);

    return s;
}

/* Append formatted string to string -- va_list version
 */
char*
str_append_vprintf (char *s, const char *format, va_list ap)
{
    char    buf[4096];
    size_t  len, oldlen;
    va_list ap2;

    va_copy(ap2, ap);
    len = vsnprintf(buf, sizeof(buf), format, ap2);
    va_end(ap2);

    if (len < sizeof(buf)) {
        return str_append_mem(s, buf, len);
    }

    oldlen = mem_len(s);
    s = mem_resize(s, oldlen + len, 1);

    va_copy(ap2, ap);
    vsnprintf(s + oldlen, len + 1, format, ap2);
    va_end(ap2);

    return s;
}

/* Concatenate several strings. Last pointer must be NULL.
 * The returned pointer must be eventually freed by mem_free
 */
char*
str_concat (const char *s, ...)
{
    va_list ap;
    char    *ret = str_dup(s);

    va_start(ap, s);
    while ((s = va_arg(ap, const char*)) != NULL) {
        ret = str_append(ret, s);
    }
    va_end(ap);

    return ret;
}

/* Check if string has a specified prefix
 */
bool
str_has_prefix (const char *s, const char *prefix)
{
    size_t l1 = strlen(s);
    size_t l2 = strlen(prefix);
    return l1 >= l2 && !memcmp(s, prefix, l2);
}

/* Check if string has a specified suffix
 */
bool
str_has_suffix (const char *s, const char *suffix)
{
    size_t l1 = strlen(s);
    size_t l2 = strlen(suffix);
    return l1 >= l2 && !memcmp(s + (l1 - l2), suffix, l2);
}

/* Remove leading and trailing white space.
 * This function modifies string in place, and returns pointer
 * to original string, for convenience
 */
char*
str_trim (char *s)
{
    size_t len = strlen(s), skip;

    while (len > 0 && safe_isspace(s[len - 1])) {
        len --;
    }

    for (skip = 0; skip < len && safe_isspace(s[skip]); skip ++) {
        ;
    }

    len -= skip;
    if (len != 0 && skip != 0) {
        memmove(s, s + skip, len);
    }
    s[len] = '\0';

    return s;
}

/* vim:ts=8:sw=4:et
 */