如何最大化代碼覆蓋率？

大家好，以下是取自unix ptx實用程序的代碼片段。我試圖最大化該實用程序的代碼覆蓋範圍，但我無法達到指定的代碼部分。無可否認，我的C技能並不像以前那樣強大。代碼部分用註釋表示，但它是朝向塊的底部。如何最大化代碼覆蓋率？

if (used_length == allocated_length) 
{ 
    allocated_length += (1 << SWALLOW_REALLOC_LOG); 
    block->start 
    = (char *) xrealloc (block->start, allocated_length); 
}

任何幫助解釋指示部分，以覆蓋該塊將不勝感激。

/* Reallocation step when swallowing non regular files. The value is not 
    the actual reallocation step, but its base two logarithm. */ 
#define SWALLOW_REALLOC_LOG 12 

static void swallow_file_in_memory (const char *file_name, BLOCK *block) 
{ 
    int file_handle;  /* file descriptor number */ 
    struct stat stat_block; /* stat block for file */ 
    size_t allocated_length; /* allocated length of memory buffer */ 
    size_t used_length;  /* used length in memory buffer */ 
    int read_length;  /* number of character gotten on last read */ 

    /* As special cases, a file name which is NULL or "-" indicates standard 
    input, which is already opened. In all other cases, open the file from 
    its name. */ 
    bool using_stdin = !file_name || !*file_name || strcmp (file_name, "-") == 0; 
    if (using_stdin) 
    file_handle = STDIN_FILENO; 
    else 
    if ((file_handle = open (file_name, O_RDONLY)) < 0) 
     error (EXIT_FAILURE, errno, "%s", file_name); 

    /* If the file is a plain, regular file, allocate the memory buffer all at 
    once and swallow the file in one blow. In other cases, read the file 
    repeatedly in smaller chunks until we have it all, reallocating memory 
    once in a while, as we go. */ 

    if (fstat (file_handle, &stat_block) < 0) 
    error (EXIT_FAILURE, errno, "%s", file_name); 

    if (S_ISREG (stat_block.st_mode)) 
    { 
     size_t in_memory_size; 

     block->start = (char *) xmalloc ((size_t) stat_block.st_size); 

     if ((in_memory_size = read (file_handle, 
        block->start, (size_t) stat_block.st_size)) 
     != stat_block.st_size) 
    { 
     error (EXIT_FAILURE, errno, "%s", file_name); 
    } 
     block->end = block->start + in_memory_size; 
    } 
    else 
    { 
     block->start = (char *) xmalloc ((size_t) 1 << SWALLOW_REALLOC_LOG); 
     used_length = 0; 
     allocated_length = (1 << SWALLOW_REALLOC_LOG); 

     while (read_length = read (file_handle, 
       block->start + used_length, 
       allocated_length - used_length), 
     read_length > 0) 
    { 
     used_length += read_length; 
     /* Cannot cover from this point...*/ 
     if (used_length == allocated_length) 
     { 
      allocated_length += (1 << SWALLOW_REALLOC_LOG); 
      block->start 
     = (char *) xrealloc (block->start, allocated_length); 
     } 
     /* ...to this point. */ 
    } 

     if (read_length < 0) 
    error (EXIT_FAILURE, errno, "%s", file_name); 

     block->end = block->start + used_length; 
    } 

    /* Close the file, but only if it was not the standard input. */ 

    if (! using_stdin && close (file_handle) != 0) 
    error (EXIT_FAILURE, errno, "%s", file_name); 
}

來源

2010-03-24 naivedeveloper