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テキスト ファイルの読み取り

この例では、関数 fopen/fread/fclose を使用してディスクからファイルを読み取る MATLAB コードからスタンドアロン C ライブラリを生成する方法を示します。

関数 readfile について

関数 readfile.m は、入力としてファイル名 (またはパス) を取得し、ファイルの内容を含む文字列を返します。

type readfile
% y = readfile(filename)
% Read file 'filename' and return a MATLAB string with the contents
% of the file.
function y = readfile(filename) %#codegen

% Put class and size constraints on function input.
assert(isa(filename, 'char'));
assert(size(filename, 1) == 1);
assert(size(filename, 2) <= 1024);

% Call fopen(filename 'r'), but we need to convert the MATLAB
% string into a C type string (which is the same string with the
% NUL (\0) string terminator).
f = fopen(filename, 'r');

% Call fseek(f, 0, SEEK_END) to set file position to the end of
% the file.
fseek(f, 0, 'eof');

% Call ftell(f) which will return the length of the file in bytes
% (as current file position is at the end of the file).
filelen = int32(ftell(f));

% Reset current file position
fseek(f,0,'bof');

% Initialize a buffer
maxBufferSize = int32(2^16);
buffer = zeros(1, maxBufferSize,'uint8');

% Remaining is the number of bytes to read (from the file)
remaining = filelen;

% Index is the current position to read into the buffer
index = int32(1);

while remaining > 0
    % Buffer overflow?
    if remaining + index > size(buffer,2)
        fprintf('Attempt to read file which is bigger than internal buffer.\n');
        fprintf('Current buffer size is %d bytes and file size is %d bytes.\n', maxBufferSize, filelen);
        break
    end
    % Read as much as possible from the file into internal buffer

    [dataRead, nread] = fread(f,remaining, 'char');
    buffer(index:index+nread-1) = dataRead;
    n = int32(nread);
    if n == 0
        % Nothing more to read
        break;
    end
    % Did something went wrong when reading?
    if n < 0
        fprintf('Could not read from file: %d.\n', n);
        break;
    end
    % Update state variables
    remaining = remaining - n;
    index = index + n;
end

% Close file
fclose(f);

y = char(buffer(1:index));

検定に使用する MEX 関数の生成

codegen コマンドを使用して MEX 関数を生成します。

codegen readfile

C コードを生成する前に、MATLAB で MEX 関数をテストして、その関数が元の MATLAB コードと機能的に等価であることと実行時のエラーが発生しないことを確認しなければなりません。既定で、codegen は、現在のフォルダーに readfile_mex という名前の MEX 関数を生成します。これにより、MATLAB コードと MEX 関数をテストして結果を比較することができます。

MEX 関数の実行

生成された MEX 関数を呼び出し、返された文字列のサイズと最初の 100 文字を表示します。

y = readfile_mex('readfile.m');
size(y)
ans = 1×2

           1        1857

y(1:100)
ans = 
    '% y = readfile(filename)
     % Read file 'filename' and return a MATLAB string with the contents
     % of th'

C コードの生成

codegen -config:lib readfile

-config cfg オプションを指定して codegen を使用すると、スタンドアロン C ライブラリが生成されます。

生成されたコードの確認

既定では、ライブラリ用に生成されたコードは codegen/lib/readfile/ フォルダーにあります。

ファイルは、以下のとおりです。

dir codegen/lib/readfile/
.                      readfile.c             readfile_initialize.o  
..                     readfile.h             readfile_ref.rsp       
.gitignore             readfile.o             readfile_rtw.mk        
buildInfo.mat          readfile_data.c        readfile_rtwutil.c     
codeInfo.mat           readfile_data.h        readfile_rtwutil.h     
codedescriptor.dmr     readfile_data.o        readfile_rtwutil.o     
compileInfo.mat        readfile_emxAPI.c      readfile_terminate.c   
defines.txt            readfile_emxAPI.h      readfile_terminate.h   
examples               readfile_emxAPI.o      readfile_terminate.o   
fileManager.c          readfile_emxutil.c     readfile_types.h       
fileManager.h          readfile_emxutil.h     rtw_proj.tmw           
fileManager.o          readfile_emxutil.o     rtwtypes.h             
interface              readfile_initialize.c  
readfile.a             readfile_initialize.h  

関数 readfile.c の C コードの検査

type codegen/lib/readfile/readfile.c
/*
 * File: readfile.c
 *
 * MATLAB Coder version            : 5.1
 * C/C++ source code generated on  : 24-Aug-2020 19:20:25
 */

/* Include Files */
#include "readfile.h"
#include "fileManager.h"
#include "readfile_data.h"
#include "readfile_emxutil.h"
#include "readfile_initialize.h"
#include "readfile_rtwutil.h"
#include "readfile_types.h"
#include <stddef.h>
#include <stdio.h>
#include <string.h>

/* Function Definitions */
/*
 * Put class and size constraints on function input.
 * Arguments    : const char filename_data[]
 *                const int filename_size[2]
 *                emxArray_char_T *y
 * Return Type  : void
 */
void readfile(const char filename_data[], const int filename_size[2],
              emxArray_char_T *y)
{
  FILE * filestar;
  int wherefrom;
  long position_t;
  size_t nBytes;
  size_t numReadSizeT;
  emxArray_uint8_T *A;
  double position;
  int b_index;
  int bytesOut;
  int i;
  int num2Read;
  int numRead;
  int other2Read;
  int remaining;
  short bdims_idx_0;
  unsigned char buffer[65536];
  char buf_data[1024];
  signed char fileid;
  boolean_T exitg1;
  if (!isInitialized_readfile) {
    readfile_initialize();
  }

  /*  y = readfile(filename) */
  /*  Read file 'filename' and return a MATLAB string with the contents */
  /*  of the file. */
  /*  Call fopen(filename 'r'), but we need to convert the MATLAB */
  /*  string into a C type string (which is the same string with the */
  /*  NUL (\0) string terminator). */
  fileid = cfopen(filename_data, filename_size, "rb");

  /*  Call fseek(f, 0, SEEK_END) to set file position to the end of */
  /*  the file. */
  wherefrom = SEEK_END;
  filestar = fileManager(fileid);
  if ((fileid == 0) || (fileid == 1) || (fileid == 2)) {
    filestar = NULL;
  }

  if (!(filestar == NULL)) {
    fseek(filestar, (long int)0.0, wherefrom);
  }

  /*  Call ftell(f) which will return the length of the file in bytes */
  /*  (as current file position is at the end of the file). */
  filestar = fileManager(fileid);
  if ((fileid == 0) || (fileid == 1) || (fileid == 2)) {
    filestar = NULL;
  }

  if (filestar == NULL) {
    position = -1.0;
  } else {
    position_t = ftell(filestar);
    position = (double)position_t;
  }

  position = rt_roundd_snf(position);
  if (position < 2.147483648E+9) {
    if (position >= -2.147483648E+9) {
      i = (int)position;
    } else {
      i = MIN_int32_T;
    }
  } else if (position >= 2.147483648E+9) {
    i = MAX_int32_T;
  } else {
    i = 0;
  }

  /*  Reset current file position */
  wherefrom = SEEK_SET;
  filestar = fileManager(fileid);
  if ((fileid == 0) || (fileid == 1) || (fileid == 2)) {
    filestar = NULL;
  }

  if (!(filestar == NULL)) {
    fseek(filestar, (long int)0.0, wherefrom);
  }

  /*  Initialize a buffer */
  memset(&buffer[0], 0, 65536U * sizeof(unsigned char));

  /*  Remaining is the number of bytes to read (from the file) */
  remaining = i;

  /*  Index is the current position to read into the buffer */
  b_index = 1;
  emxInit_uint8_T(&A, 1);
  exitg1 = false;
  while ((!exitg1) && (remaining > 0)) {
    /*  Buffer overflow? */
    if (b_index > MAX_int32_T - remaining) {
      other2Read = MAX_int32_T;
    } else {
      other2Read = remaining + b_index;
    }

    if (other2Read > 65536) {
      printf("Attempt to read file which is bigger than internal buffer.\n");
      fflush(stdout);
      printf("Current buffer size is %d bytes and file size is %d bytes.\n",
             65536, i);
      fflush(stdout);
      exitg1 = true;
    } else {
      /*  Read as much as possible from the file into internal buffer */
      nBytes = sizeof(char);
      filestar = fileManager(fileid);
      if ((fileid == 0) || (fileid == 1) || (fileid == 2)) {
        filestar = NULL;
      }

      if (filestar == NULL) {
        A->size[0] = 0;
        bytesOut = 0;
      } else {
        num2Read = A->size[0];
        A->size[0] = remaining;
        emxEnsureCapacity_uint8_T(A, num2Read);
        if (remaining > 1024) {
          bdims_idx_0 = 1024;
        } else {
          bdims_idx_0 = (short)remaining;
        }

        bytesOut = 0;
        numRead = 1;
        while ((bytesOut < remaining) && (numRead > 0)) {
          num2Read = bdims_idx_0;
          other2Read = remaining - bytesOut;
          if (bdims_idx_0 > other2Read) {
            num2Read = other2Read;
          }

          numRead = 0;
          other2Read = 1;
          while ((numRead < num2Read) && (other2Read > 0)) {
            numReadSizeT = fread(&buf_data[numRead], nBytes, num2Read - numRead,
                                 filestar);
            other2Read = (int)numReadSizeT;
            numRead += (int)numReadSizeT;
          }

          for (other2Read = 0; other2Read < numRead; other2Read++) {
            A->data[other2Read + bytesOut] = (unsigned char)buf_data[other2Read];
          }

          bytesOut += numRead;
        }

        num2Read = bytesOut + 1;
        numRead = A->size[0];
        for (other2Read = num2Read; other2Read <= numRead; other2Read++) {
          A->data[other2Read - 1] = 0U;
        }

        if (bytesOut < remaining) {
          num2Read = A->size[0];
          if (1 > bytesOut) {
            A->size[0] = 0;
          } else {
            A->size[0] = bytesOut;
          }

          emxEnsureCapacity_uint8_T(A, num2Read);
        }
      }

      position = (double)b_index + (double)bytesOut;
      if (position < 2.147483648E+9) {
        if (position >= -2.147483648E+9) {
          num2Read = (int)position;
        } else {
          num2Read = MIN_int32_T;
        }
      } else {
        num2Read = MAX_int32_T;
      }

      if (b_index > num2Read - 1) {
        numRead = -1;
        num2Read = -1;
      } else {
        numRead = b_index - 2;
        num2Read -= 2;
      }

      other2Read = num2Read - numRead;
      for (num2Read = 0; num2Read < other2Read; num2Read++) {
        buffer[(numRead + num2Read) + 1] = A->data[num2Read];
      }

      if (bytesOut == 0) {
        /*  Nothing more to read */
        exitg1 = true;
      } else {
        /*  Did something went wrong when reading? */
        if (bytesOut < 0) {
          printf("Could not read from file: %d.\n", bytesOut);
          fflush(stdout);
          exitg1 = true;
        } else {
          /*  Update state variables */
          remaining -= bytesOut;
          if ((b_index < 0) && (bytesOut < MIN_int32_T - b_index)) {
            b_index = MIN_int32_T;
          } else if ((b_index > 0) && (bytesOut > MAX_int32_T - b_index)) {
            b_index = MAX_int32_T;
          } else {
            b_index += bytesOut;
          }
        }
      }
    }
  }

  emxFree_uint8_T(&A);

  /*  Close file */
  cfclose(fileid);
  i = y->size[0] * y->size[1];
  y->size[0] = 1;
  y->size[1] = b_index;
  emxEnsureCapacity_char_T(y, i);
  for (i = 0; i < b_index; i++) {
    y->data[i] = (signed char)buffer[i];
  }
}

/*
 * File trailer for readfile.c
 *
 * [EOF]
 */