在 PHP 中读取二进制文件

Question

是否有关于如何读取二进制文件的全面信息？我在 PHP 网站 (http://www.php.net/manual/en/function.pack.php) 上找到了信息，但我很难理解如何处理“typedef struct”和结构使用。

我有一个很长的二进制文件，里面有很多块，每个块都可以用 C 结构来表示。这个 C 结构有各种“typedef 结构”，类似于我在下面提出的：

typedef struct
{ 
 unsigned char Day;
 unsigned char Month;
 unsigned char Year;
} DATE_OF_BIRTH;
#define USER_TYPE 5
DATE_OF_BIRTH Birth[2];\

---

编辑：

我在下面有一个结构，这是一个更大结构的一部分

typedef struct FILE_HEADER_tag
{
    int Type;
    int Version;
    unsigned long Model;
    unsigned long Number;
    int Class;

    int TemplateLoaded;
    char TemplateName[32];
    RTC_TIME_DATE StartTime;
    RTC_TIME_DATE CurrentCal;
    RTC_TIME_DATE OriginalCal;
    TEMPLATE_SETTINGS;
    int EndType;
} FILE_HEADER;

typedef struct
{
 unsigned char Second;
 unsigned char Minute;
 unsigned char Hour;
 unsigned char Day;
 unsigned char Month;
 unsigned char Year;
} RTC_TIME_DATE;

二进制文件充满了换行符，我能够解码它的第一行，它返回正确：类型、版本、型号、编号和一个类。我想我还解码了两个 next 变量，但我不确定，因为 StartTime 返回一些乱码。

目前我正在遍历二进制文件中的行并尝试解压缩每一行：

$i = 1;
while (($line = fgets($handle)) !== false) {
    // process the line read.
    var_dump($line);
    if($i == 1) {
        $unpacked = unpack('iType/iVersion/LModel/LNumber/iClass/iTemplateLoaded', $line );
    }if($i == 2) {
        $i++;
        continue;
    }if($i == 3) { 
        $unpacked = unpack('C32TemplateName/CStartTime[Second]/CStartTime[Minute]/CStartTime[Hour]/CStartTime[Day]/CStartTime[Month]/CStartTime[Year]', $line);
    }

    print "<pre>";
    var_dump($unpacked);
    print "</pre>";

    $i++;

    if($i == 4) { exit; }
}

Answer 1

我不太确定你想在这里实现什么。如果你有一个从上面的 c 代码生成的二进制文件，那么你可以像这样读取和解压缩它的内容：

// get size of the binary file
$filesize = filesize('filename.bin');
// open file for reading in binary mode
$fp = fopen('filename.bin', 'rb');
// read the entire file into a binary string
$binary = fread($fp, $filesize);
// finally close the file
fclose($fp);

// unpack the data - notice that we create a format code using 'C%d'
// that will unpack the size of the file in unsigned chars
$unpacked = unpack(sprintf('C%d', $filesize), $binary);

// reset array keys
$unpacked = array_values($unpacked);

// this variable holds the size of *one* structure in the file
$block_size = 3;
// figure out the number of blocks in the file
$block_count = $file_size/$block_size;

// you now should have an array where each element represents a
// unsigned char from the binary file, so to display Day, Month and Year
for ($i = 0, $j = 0; $i < $block_count; $i++, $j+=$block_size) {
   print 'Day: ' . $unpacked[$j] . '<br />';
   print 'Month: ' . $unpacked[$j+1] . '<br />';
   print 'Year: ' . $unpacked[$j+2] . '<br /><br />';
}

当然你也可以创建一个对象来保存数据：

class DATE_OF_BIRTH {
  public $Day;
  public $Month;
  public $Year;

  public function __construct($Day, $Month, $Year) {
      $this->Day = $Day;
      $this->Month = $Month;
      $this->Year = $Year;
  }
}

$Birth = [];

for ($i = 0, $j = 0; $i < $block_count; $i++, $j+=$block_size) {
   $Birth[] = new DATE_OF_BIRTH(
       $unpacked[$j], 
       $unpacked[$j+1], 
       $unpacked[$j+2]
   );
}

另一种方法是在每个第三个元素处对其进行切片：

$Birth = [];    

for ($i = 0; $i < $block_count; $i++) {
  // slice one read structure from the array
  $slice = array_slice($unpacked, $i * $block_size, $block_size);

  // combine the extracted array containing Day, Month and Year
  // with the appropriate keys
  $slice = array_combine(array('Day', 'Month', 'Year'), $slice);

  $Birth[] = $slice;
}

您还应该知道，这可能会变得更加复杂，具体取决于您的结构包含的数据，请考虑以下小型 c 程序：

#include <stdio.h>
#include <stdlib.h>

// pack structure members with a 1 byte aligment
struct __attribute__((__packed__)) person_t {
  char name[5];
  unsigned int age;
};

struct person_t persons[2] = {
  {
    { 
      'l', 'i', 's', 'a', 0 
    },
    16
  },
  {
    { 
       'c', 'o', 'r', 'n', 0 
    },
    52
  }
};

int main(int argc, char** argv) {
  FILE* fp = fopen("binary.bin", "wb");
  fwrite(persons, sizeof(persons), 1, fp);
  fclose(fp);
  return 0;
}

上面将每个打包的结构写入文件binary.bin，大小正好是18字节。为了更好地掌握对齐/包装，您可以查看此帖子：Structure padding and packing

然后在您的 php 代码中，您可以像这样在循环中读取每个块：

$filesize = filesize("binary.bin");
$fp = fopen("binary.bin", "rb");
$binary = fread($fp, $filesize);
fclose($fp);

// this variable holds the size of *one* structure
$block_size = 9;
$num_blocks = $filesize/$block_size;

// extract each block in a loop from the binary string
for ($i = 0, $offset = 0; $i < $num_blocks; $i++, $offset += $block_size) {
   $unpacked_block = unpack("C5char/Iint", substr($binary, $offset));
   $unpacked_block = array_values($unpacked_block);

   // walk over the 'name' part and get the ascii value
   array_walk($unpacked_block, function(&$item, $key) {
      if($key < 5) {
        $item = chr($item);
      }
   });
   $name = implode('', array_slice($unpacked_block, 0, 5));
   $age = implode('', array_slice($unpacked_block, 5, 1));
   print 'name: ' . $name . '<br />';
   print 'age: ' . $age . '<br />';
}