tesseract/ccutil/strngs.cpp

/**********************************************************************
 * File:        strngs.c  (Formerly strings.c)
 * Description: STRING class functions.
 * Author:					Ray Smith
 * Created:					Fri Feb 15 09:13:30 GMT 1991
 *
 * (C) Copyright 1991, Hewlett-Packard Ltd.
 ** 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          "mfcpch.h"     //precompiled headers
#include          "tprintf.h"
#include          "strngs.h"

/**********************************************************************
 * DataCache for reducing initial allocations, such as the default
 * constructor. The memory in this cache is not special, it is just
 * held locally rather than freeing. Only blocks with the default
 * capacity are considered for the cache.
 *
 * In practice it does not appear that this cache grows very big,
 * so even 2-4 elements are probably sufficient to realize most
 * gains.
 *
 * The cache is maintained globally with a global destructor to
 * avoid memory leaks being reported on exit.
 **********************************************************************/
// kDataCacheSize is cache of last n min sized buffers freed for
// cheap recyling
const int kDataCacheSize = 8;  // max number of buffers cached

#if 1
#define CHECK_INVARIANT(s)  // EMPTY
#else
static void check_used_(int len, const char *s) {
  bool ok;

  if (len == 0)
    ok = (s == NULL);
  else
    ok = (len == (strlen(s) + 1));

  if (!ok)
    abort();
}

#define CHECK_INVARIANT(s)  check_used_(s->GetHeader()->used_, s->string())
#endif

// put recycled buffers into a class so we can destroy it on exit
class DataCache {
 public:
  DataCache() {
    top_ = 0;
  }
  ~DataCache() {
    while (--top_ >= 0)
        free_string((char *)stack_[top_]);
  }

  // Allocate a buffer out of this cache.
  // Returs NULL if there are no cached buffers.
  // The buffers in the cache can be freed using string_free.
  void* alloc() {
    if (top_ == 0)
      return NULL;

    return stack_[--top_];
  }

  // Free pointer either by caching it on the stack of pointers
  // or freeing it with string_free if there isnt space left to cache it.
  // s should have capacity kMinCapacity.
  void free(void* p) {
    if (top_ == kDataCacheSize)
      free_string((char *)p);
    else
      stack_[top_++] = p;
  }

  // Stack of discarded but not-yet freed pointers.
  void* stack_[kDataCacheSize];

  // Top of stack, points to element after last cached pointer
  int   top_;
};

static DataCache MinCapacityDataCache;


/**********************************************************************
 * STRING_HEADER provides metadata about the allocated buffer,
 * including total capacity and how much used (strlen with '\0').
 *
 * The implementation hides this header at the start of the data
 * buffer and appends the string on the end to keep sizeof(STRING)
 * unchanged from earlier versions so serialization is not affected.
 *
 * The collection of MACROS provide different implementations depending
 * on whether the string keeps track of its strlen or not so that this
 * feature can be added in later when consumers dont modifify the string
 **********************************************************************/

// Smallest string to allocate by default
const int kMinCapacity = 16;

char* STRING::AllocData(int used, int capacity) {
  if ((capacity != kMinCapacity)
      || ((data_ = (STRING_HEADER *)MinCapacityDataCache.alloc()) == NULL))
    data_ = (STRING_HEADER *)alloc_string(capacity + sizeof(STRING_HEADER));

  // header is the metadata for this memory block
  STRING_HEADER* header = GetHeader();
  header->capacity_ = capacity;
  header->used_ = used;
  return GetCStr();
}

void STRING::DiscardData() {
  STRING_HEADER* header = GetHeader();
  if (header->capacity_ == kMinCapacity)
    MinCapacityDataCache.free(data_);
  else
    free_string((char *)data_);
}

// This is a private method; ensure FixHeader is called (or used_ is well defined)
// beforehand
char* STRING::ensure_cstr(inT32 min_capacity) {
  STRING_HEADER* orig_header = GetHeader();
  if (min_capacity <= orig_header->capacity_)
    return ((char *)this->data_) + sizeof(STRING_HEADER);

  // if we are going to grow bigger, than double our existing
  // size, but if that still is not big enough then keep the
  // requested capacity
  if (min_capacity < 2 * orig_header->capacity_)
    min_capacity = 2 * orig_header->capacity_;

  int alloc = sizeof(STRING_HEADER) + min_capacity;
  STRING_HEADER* new_header = (STRING_HEADER*)(alloc_string(alloc));

  memcpy(&new_header[1], GetCStr(), orig_header->used_);
  new_header->capacity_ = min_capacity;
  new_header->used_ = orig_header->used_;

  // free old memory, then rebind to new memory
  DiscardData();
  data_ = new_header;

  CHECK_INVARIANT(this);
  return ((char *)data_) + sizeof(STRING_HEADER);
}

// This is const, but is modifying a mutable field
// this way it can be used on const or non-const instances.
void STRING::FixHeader() const {
  const STRING_HEADER* header = GetHeader();
  if (header->used_ < 0)
    header->used_ = strlen(GetCStr()) + 1;
}


STRING::STRING() {
  // 0 indicates old NULL -- it doesnt even have '\0'
  AllocData(0, kMinCapacity);
}

STRING::STRING(const STRING& str) {
  str.FixHeader();
  const STRING_HEADER* str_header  = str.GetHeader();
  int   str_used  = str_header->used_;
  char *this_cstr = AllocData(str_used, str_used);
  memcpy(this_cstr, str.GetCStr(), str_used);
  CHECK_INVARIANT(this);
}

STRING::STRING(const char* cstr) {
  if (cstr == NULL) {
    AllocData(0, 0);
  } else {
    int len = strlen(cstr) + 1;
    char* this_cstr = AllocData(len, len);
    memcpy(this_cstr, cstr, len);
  }
  CHECK_INVARIANT(this);
}

STRING::~STRING() {
  DiscardData();
}

BOOL8 STRING::contains(const char c) const {
  return (c != '\0') && (strchr (GetCStr(), c) != NULL);
}

inT32 STRING::length() const {
  FixHeader();
  return GetHeader()->used_ - 1;
}

const char* STRING::string() const {
  const STRING_HEADER* header = GetHeader();
  if (header->used_ == 0)
    return NULL;

  // mark header length unreliable because tesseract might
  // cast away the const and mutate the string directly.
  header->used_ = -1;
  return GetCStr();
}

/******
 * The STRING_IS_PROTECTED interface adds additional support to migrate
 * code that needs to modify the STRING in ways not otherwise supported
 * without violating encapsulation.
 *
 * Also makes the [] operator return a const so it is immutable
 */
#if STRING_IS_PROTECTED
const char& STRING::operator[](inT32 index) const {
  return GetCStr()[index];
}

void STRING::insert_range(inT32 index, const char* str, int len) {
  // if index is outside current range, then also grow size of string
  // to accmodate the requested range.
  STRING_HEADER* this_header = GetHeader();
  int used = this_header->used_;
  if (index > used)
    used = index;

  char* this_cstr = ensure_cstr(used + len + 1);
  if (index < used) {
    // move existing string from index to '\0' inclusive.
    memmove(this_cstr + index + len,
           this_cstr + index,
           this_header->used_ - index);
  } else if (len > 0) {
    // We are going to overwrite previous null terminator, so write the new one.
    this_cstr[this_header->used_ + len - 1] = '\0';

    // If the old header did not have the terminator,
    // then we need to account for it now that we've added it.
    // Otherwise it was already accounted for; we just moved it.
    if (this_header->used_ == 0)
      ++this_header->used_;
  }

  // Write new string to index.
  // The string is already terminated from the conditions above.
  memcpy(this_cstr + index, str, len);
  this_header->used_ += len;

  CHECK_INVARIANT(this);
}

void STRING::erase_range(inT32 index, int len) {
  char* this_cstr = GetCStr();
  STRING_HEADER* this_header = GetHeader();

  memcpy(this_cstr+index, this_cstr+index+len,
         this_header->used_ - index - len);
  this_header->used_ -= len;
  CHECK_INVARIANT(this);
}

void STRING::truncate_at(inT32 index) {
  char* this_cstr = ensure_cstr(index);
  this_cstr[index] = '\0';
  GetHeader()->used_ = index;
  CHECK_INVARIANT(this);
}

#else
char& STRING::operator[](inT32 index) const {
  // Code is casting away this const and mutating the string,
  // so mark used_ as -1 to flag it unreliable.
  GetHeader()->used_ = -1;
  return ((char *)GetCStr())[index];
}
#endif

BOOL8 STRING::operator==(const STRING& str) const {
  FixHeader();
  str.FixHeader();
  const STRING_HEADER* str_header = str.GetHeader();
  const STRING_HEADER* this_header = GetHeader();
  int this_used = this_header->used_;
  int str_used  = str_header->used_;

  return (this_used == str_used)
          && (memcmp(GetCStr(), str.GetCStr(), this_used) == 0);
}

BOOL8 STRING::operator!=(const STRING& str) const {
  FixHeader();
  str.FixHeader();
  const STRING_HEADER* str_header = str.GetHeader();
  const STRING_HEADER* this_header = GetHeader();
  int this_used = this_header->used_;
  int str_used  = str_header->used_;

  return (this_used != str_used)
         || (memcmp(GetCStr(), str.GetCStr(), this_used) != 0);
}

BOOL8 STRING::operator!=(const char* cstr) const {
  FixHeader();
  const STRING_HEADER* this_header = GetHeader();

  if (cstr == NULL)
    return this_header->used_ > 1;  // either '\0' or NULL
  else {
    inT32 length = strlen(cstr) + 1;
    return (this_header->used_ != length)
            || (memcmp(GetCStr(), cstr, length) != 0);
  }
}

STRING& STRING::operator=(const STRING& str) {
  str.FixHeader();
  const STRING_HEADER* str_header = str.GetHeader();
  int   str_used = str_header->used_;

  GetHeader()->used_ = 0;  // clear since ensure doesnt need to copy data
  char* this_cstr = ensure_cstr(str_used);
  STRING_HEADER* this_header = GetHeader();

  memcpy(this_cstr, str.GetCStr(), str_used);
  this_header->used_ = str_used;

  CHECK_INVARIANT(this);
  return *this;
}

STRING & STRING::operator+=(const STRING& str) {
  FixHeader();
  str.FixHeader();
  const STRING_HEADER* str_header = str.GetHeader();
  const char* str_cstr = str.GetCStr();
  int  str_used  = str_header->used_;
  int  this_used = GetHeader()->used_;
  char* this_cstr = ensure_cstr(this_used + str_used);

  STRING_HEADER* this_header = GetHeader();  // after ensure for realloc

  if (this_used > 1) {
    memcpy(this_cstr + this_used - 1, str_cstr, str_used);
    this_header->used_ += str_used - 1;  // overwrite '\0'
  } else {
    memcpy(this_cstr, str_cstr, str_used);
    this_header->used_ = str_used;
  }

  CHECK_INVARIANT(this);
  return *this;
}

void STRING::prep_serialise() {
  // WARNING
  // This method should only be called on a shallow bitwise copy
  // by the serialise() method (see serialis.h).
  FixHeader();
  data_ = (STRING_HEADER *)GetHeader()->used_;
}


void STRING::dump(FILE* f) {
  FixHeader();
  serialise_bytes (f, data_, GetHeader()->used_);
}

void STRING::de_dump(FILE* f) {
  char *instring;            //input from read
  fprintf(stderr, "de_dump\n");
  instring = (char *)de_serialise_bytes(f, (ptrdiff_t)data_);
  int len = strlen(instring) + 1;

  char* this_cstr = AllocData(len, len);
  STRING_HEADER* this_header = GetHeader();

  memcpy(this_cstr, instring, len);
  this_header->used_ = len;

  free_mem(instring);
  CHECK_INVARIANT(this);
}


STRING & STRING::operator=(const char* cstr) {
  STRING_HEADER* this_header = GetHeader();
  if (cstr) {
    int len = strlen(cstr) + 1;

    this_header->used_ = 0;  // dont bother copying data if need to realloc
    char* this_cstr = ensure_cstr(len);
    this_header = GetHeader();  // for realloc
    memcpy(this_cstr, cstr, len);
    this_header->used_ = len;
  }
  else {
    // Reallocate to zero capacity buffer, consistent with the corresponding
    // copy constructor.
    DiscardData();
    AllocData(0, 0);
  }

  CHECK_INVARIANT(this);
  return *this;
}


STRING STRING::operator+(const STRING& str) const {
  STRING result(*this);
  result += str;

  CHECK_INVARIANT(this);
  return result;
}


STRING STRING::operator+(const char ch) const {
  STRING result;
  FixHeader();
  const STRING_HEADER* this_header = GetHeader();
  int this_used = this_header->used_;
  char* result_cstr = result.ensure_cstr(this_used + 1);
  STRING_HEADER* result_header = result.GetHeader();
  int result_used = result_header->used_;

  // copies '\0' but we'll overwrite that
  memcpy(result_cstr, GetCStr(), this_used);
  result_cstr[result_used] = ch;      // overwrite old '\0'
  result_cstr[result_used + 1] = '\0';  // append on '\0'
  ++result_header->used_;

  CHECK_INVARIANT(this);
  return result;
}


STRING&  STRING::operator+=(const char *str) {
  if (!str || !*str)  // empty string has no effect
    return *this;

  FixHeader();
  int len = strlen(str) + 1;
  int this_used = GetHeader()->used_;
  char* this_cstr = ensure_cstr(this_used + len);
  STRING_HEADER* this_header = GetHeader();  // after ensure for realloc

  // if we had non-empty string then append overwriting old '\0'
  // otherwise replace
  if (this_used > 0) {
    memcpy(this_cstr + this_used - 1, str, len);
    this_header->used_ += len - 1;
  } else {
    memcpy(this_cstr, str, len);
    this_header->used_ = len;
  }

  CHECK_INVARIANT(this);
  return *this;
}


STRING& STRING::operator+=(const char ch) {
  if (ch == '\0')
    return *this;

  FixHeader();
  int   this_used = GetHeader()->used_;
  char* this_cstr = ensure_cstr(this_used + 1);
  STRING_HEADER* this_header = GetHeader();

  if (this_used > 0)
    --this_used; // undo old empty null if there was one

  this_cstr[this_used++] = ch;   // append ch to end
  this_cstr[this_used++] = '\0'; // append '\0' after ch
  this_header->used_ = this_used;

  CHECK_INVARIANT(this);
  return *this;
}