astring.c

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/***********************************************************************
 Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
***********************************************************************/
 
/***********************************************************************
  Allocated/allocatable strings
  original author: David Pfitzner <dwp@mso.anu.edu.au>
 
  A common technique is to have some memory dynamically allocated
  (using malloc etc), to avoid compiled-in limits, but only allocate
  enough space as initially needed, and then realloc later if/when
  require more space. Typically, the realloc is made a bit more than
  immediately necessary, to avoid frequent reallocs if the object
  grows incrementally. Also, don't usually realloc at all if the
  object shrinks. This is straightforward, but just requires a bit
  of book-keeping to keep track of how much has been allocated etc.
  This module provides some tools to make this a bit easier.
 
  This is deliberately simple and light-weight. The user is allowed
  full access to the struct elements rather than use accessor
  functions etc.
 
  Note one potential hazard: when the size is increased (astr_reserve()),
  realloc (really fc_realloc()) is used, which retains any data which
  was there previously, _but_: any external pointers into the allocated
  memory may then become wild. So you cannot safely use such external
  pointers into the astring data, except strictly between times when
  the astring size may be changed.
 
  There are two ways of getting the resulting string as a char *:
 
   - astr_str() returns a const char *. This should not be modified
     or freed by the caller; the storage remains owned by the
     struct astring, which should be freed with astr_free().
 
   - astr_to_str() returns a char * and destroys the struct astring.
     Responsibility for freeing the storage becomes the caller's.
 
  One pattern for using astr_str() is to replace static buffers in
  functions that return a pointer to static storage. Where previously
  you would have had e.g. "static struct buf[128]" with an arbitrary
  size limit, you can have "static struct astring buf", and reuse
  the same astring on subsequent calls; the caller should behave
  the same (only reading the string and not freeing it).
 
***********************************************************************/
 
#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif
 
#include "fc_prehdrs.h"
 
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
 
/* utility */
#include "fcintl.h"
#include "fcthread.h"
#include "log.h"                /* fc_assert() */
#include "mem.h"
#include "support.h"            /* fc_vsnprintf(), fc_strlcat() */
 
#include "astring.h"
 
#define str     _private_str_
#define n       _private_n_
#define n_alloc _private_n_alloc_
 
static const struct astring zero_astr = ASTRING_INIT;
static char *astr_buffer = nullptr;
static size_t astr_buffer_alloc = 0;
 
static fc_mutex astr_mutex;
 
static inline char *astr_buffer_get(size_t *alloc);
static inline char *astr_buffer_grow(size_t request, size_t *alloc);
static void astr_buffer_free(void);
 
/************************************************************************/
static inline char *astr_buffer_get(size_t *alloc)
{
  if (astr_buffer == nullptr) {
    astr_buffer_alloc = 4096;
    astr_buffer = fc_malloc(astr_buffer_alloc);
    atexit(astr_buffer_free);
  }
 
  *alloc = astr_buffer_alloc;
 
  return astr_buffer;
}
 
/************************************************************************/
static inline char *astr_buffer_grow(size_t request, size_t *alloc)
{
  if (request > astr_buffer_alloc) {
    /* We simply set buffer size to the requested one here.
     * Old implementation went on by doubling the buffer size,
     * presumably to match what low level memory handling does
     * anyway. But need to increase the buffer size is so rare
     * that we can as well call this function again, even when
     * the increase would fall within limits of what doubling
     * would have given us. */
    astr_buffer_alloc = request;
  }
  astr_buffer = fc_realloc(astr_buffer, astr_buffer_alloc);
 
  *alloc = astr_buffer_alloc;
 
  return astr_buffer;
}
 
/************************************************************************/
static void astr_buffer_free(void)
{
  free(astr_buffer);
}
 
/************************************************************************/
void astr_init(struct astring *astr)
{
  *astr = zero_astr;
}
 
/************************************************************************/
void astr_free(struct astring *astr)
{
  if (astr->n_alloc > 0) {
    fc_assert_ret(astr->str != nullptr);
    free(astr->str);
  }
 
  *astr = zero_astr;
}
 
/************************************************************************/
char *astr_to_str(struct astring *astr)
{
  char *str = astr->str;
 
  *astr = zero_astr;
 
  return str;
}
 
/************************************************************************/
void astr_reserve(struct astring *astr, size_t n)
{
  unsigned int n1;
  bool was_null = (astr->n == 0);
 
  astr->n = n;
  if (n <= astr->n_alloc) {
    return;
  }
 
  /* Allocated more if this is only a small increase on before: */
  n1 = (3 * (astr->n_alloc + 10)) / 2;
  astr->n_alloc = (n > n1) ? n : n1;
  astr->str = (char *) fc_realloc(astr->str, astr->n_alloc);
  if (was_null) {
    astr_clear(astr);
  }
}
 
/************************************************************************/
void astr_clear(struct astring *astr)
{
  if (astr->n == 0) {
    /* astr_reserve() is really astr_size(), so we don't want to reduce
     * the size. */
    astr_reserve(astr, 1);
  }
  astr->str[0] = '\0';
}
 
/************************************************************************/
static inline void astr_vadd_at(struct astring *astr, size_t at,
                                const char *format, va_list ap)
{
  char *buffer;
  size_t buffer_size;
  size_t req_len;
  va_list copy;
 
  fc_mutex_allocate(&astr_mutex);
 
  buffer = astr_buffer_get(&buffer_size);
 
  va_copy(copy, ap);
 
  req_len = fc_vsnprintf(buffer, buffer_size, format, ap);
  if (req_len + 1 > buffer_size) {
    buffer = astr_buffer_grow(req_len + 1, &buffer_size);
    /* Even if buffer is *still* too small, we fill what we can */
    req_len = fc_vsnprintf(buffer, buffer_size, format, copy);
    if (req_len > buffer_size) {
      /* What we actually got */
      req_len = buffer_size;
    }
  }
  va_end(copy);
 
  req_len += at + 1;
 
  astr_reserve(astr, req_len);
  fc_strlcpy(astr->str + at, buffer, astr->n_alloc - at);
 
  fc_mutex_release(&astr_mutex);
}
 
/************************************************************************/
void astr_set(struct astring *astr, const char *format, ...)
{
  va_list args;
 
  va_start(args, format);
  astr_vadd_at(astr, 0, format, args);
  va_end(args);
}
 
/************************************************************************/
void astr_vadd(struct astring *astr, const char *format, va_list ap)
{
  astr_vadd_at(astr, astr_len(astr), format, ap);
}
 
/************************************************************************/
void astr_add(struct astring *astr, const char *format, ...)
{
  va_list args;
 
  va_start(args, format);
  astr_vadd_at(astr, astr_len(astr), format, args);
  va_end(args);
}
 
/************************************************************************/
void astr_add_line(struct astring *astr, const char *format, ...)
{
  size_t len = astr_len(astr);
  va_list args;
 
  va_start(args, format);
  if (0 < len) {
    astr_vadd_at(astr, len + 1, format, args);
    astr->str[len] = '\n';
  } else {
    astr_vadd_at(astr, len, format, args);
  }
  va_end(args);
}
 
/************************************************************************/
void astr_break_lines(struct astring *astr, size_t desired_len)
{
  fc_break_lines(astr->str, desired_len);
}
 
/************************************************************************/
const char *astr_build_or_list(struct astring *astr,
                               const char *const *items, size_t number)
{
  fc_assert_ret_val(astr != nullptr, nullptr);
  fc_assert_ret_val(0 < number, nullptr);
  fc_assert_ret_val(items != nullptr, nullptr);
 
  if (1 == number) {
    /* TRANS: "or"-separated string list with one single item. */
    astr_set(astr, Q_("?or-list-single:%s"), *items);
  } else if (2 == number) {
    /* TRANS: "or"-separated string list with 2 items. */
    astr_set(astr, Q_("?or-list:%s or %s"), items[0], items[1]);
  } else {
    /* Estimate the space we need. */
    astr_reserve(astr, number * 64);
    /* TRANS: start of an "or"-separated string list with more than
     * two items. */
    astr_set(astr, Q_("?or-list:%s"), *items++);
    while (1 < --number) {
      /* TRANS: next elements of an "or"-separated string list with more
       * than two items. */
      astr_add(astr, Q_("?or-list:, %s"), *items++);
    }
    /* TRANS: end of an "or"-separated string list with more than
     * two items. */
    astr_add(astr, Q_("?or-list:, or %s"), *items);
  }
 
  return astr->str;
}
 
/************************************************************************/
const char *astr_build_and_list(struct astring *astr,
                                const char *const *items, size_t number)
{
  fc_assert_ret_val(astr != nullptr, nullptr);
  fc_assert_ret_val(0 < number, nullptr);
  fc_assert_ret_val(items != nullptr, nullptr);
 
  if (1 == number) {
    /* TRANS: "and"-separated string list with one single item. */
    astr_set(astr, Q_("?and-list-single:%s"), *items);
  } else if (2 == number) {
    /* TRANS: "and"-separated string list with 2 items. */
    astr_set(astr, Q_("?and-list:%s and %s"), items[0], items[1]);
  } else {
    /* Estimate the space we need. */
    astr_reserve(astr, number * 64);
    /* TRANS: start of an "and"-separated string list with more than
     * two items. */
    astr_set(astr, Q_("?and-list:%s"), *items++);
    while (1 < --number) {
      /* TRANS: next elements of an "and"-separated string list with more
       * than two items. */
      astr_add(astr, Q_("?and-list:, %s"), *items++);
    }
    /* TRANS: end of an "and"-separated string list with more than
     * two items. */
    astr_add(astr, Q_("?and-list:, and %s"), *items);
  }
 
  return astr->str;
}
 
/************************************************************************/
void astr_copy(struct astring *dest, const struct astring *src)
{
  if (astr_empty(src)) {
    astr_clear(dest);
  } else {
    astr_set(dest, "%s", src->str);
  }
}
 
/************************************************************************/
void fc_astr_init(void)
{
  fc_mutex_init(&astr_mutex);
}
 
/************************************************************************/
void fc_astr_free(void)
{
  fc_mutex_destroy(&astr_mutex);
}