fread_bytesT_fread_bytesFreadBytesFreadBytesfread_bytes (算子)

名称

fread_bytesT_fread_bytesFreadBytesFreadBytesfread_bytes — 从二进制文件读取字节。

签名

fread_bytes( : : FileHandle, NumberOfBytes : ReadData, IsEOF)

描述

算子 fread_bytesfread_bytesFreadBytesFreadBytesFreadBytesfread_bytes reads bytes from the input file defined by FileHandleFileHandleFileHandleFileHandlefileHandlefile_handle. The input file must have been opened with open_fileopen_fileOpenFileOpenFileOpenFileopen_file in binary format.

The number of bytes to be read, greater than 0, is specified as NumberOfBytesNumberOfBytesNumberOfBytesNumberOfBytesnumberOfBytesnumber_of_bytes。

The bytes that are read are returned in ReadDataReadDataReadDataReadDatareadDataread_data. IsEOFIsEOFIsEOFIsEOFisEOFis_eof is set to 1 if end of file is reached while reading the bytes from the input binary file. Otherwise, it is set to 0.

When the number of bytes to be read is larger than the number of bytes in the input binary file, the operator fread_bytesfread_bytesFreadBytesFreadBytesFreadBytesfread_bytes returns all bytes read till the end of the file in ReadDataReadDataReadDataReadDatareadDataread_data and parameter IsEOFIsEOFIsEOFIsEOFisEOFis_eof is set to 1.

If no byte can be read because the end of the file is reached, ReadDataReadDataReadDataReadDatareadDataread_data is empty and IsEOFIsEOFIsEOFIsEOFisEOFis_eof is set to 1.

执行信息

多线程类型：可重入（与非独占算子并行运行）。
多线程作用域：全局（可从任何线程调用）。
未采用并行化处理。

参数

FileHandleFileHandleFileHandleFileHandlefileHandlefile_handle (输入控制) file → (handle)

File handle.

NumberOfBytesNumberOfBytesNumberOfBytesNumberOfBytesnumberOfBytesnumber_of_bytes (输入控制) integer → (integer)

Number of bytes to be read.

ReadDataReadDataReadDataReadDatareadDataread_data (输出控制) integer-array → (integer)

Bytes read from the input binary file.

IsEOFIsEOFIsEOFIsEOFisEOFis_eof (输出控制) integer → (integer)

Indicates if end of file is reached while reading the file.

示例（HDevelop）

* Read a binary file 5 bytes at a time till EOF is reached.
open_file(Filename,'input_binary',FileHandle)
repeat
  fread_bytes(FileHandle, 5, BytesRead, IsEOF)
until (IsEOF)
close_file (FileHandle)

结果

If an input file is open in binary mode and no file read error occurs,the operator fread_bytesfread_bytesFreadBytesFreadBytesFreadBytesfread_bytes 返回 2 ( H_MSG_TRUE )。否则，将抛出异常。

可能的前趋

open_fileopen_fileOpenFileOpenFileOpenFileopen_file

可能的后继

close_fileclose_fileCloseFileCloseFileCloseFileclose_file

替代

fread_charfread_charFreadCharFreadCharFreadCharfread_char

另见

open_fileopen_fileOpenFileOpenFileOpenFileopen_file, close_fileclose_fileCloseFileCloseFileCloseFileclose_file, fwrite_bytesfwrite_bytesFwriteBytesFwriteBytesFwriteBytesfwrite_bytes

模块

基础

算子