Bob Nystrom
3746b56ed9
Extend File.readBytes with a second overload accepting an offset argument, allowing reads to start at any byte position from the beginning of the file. The existing single-argument variant now delegates to the new two-argument version with offset 0. Validation for the offset parameter mirrors the existing count checks, aborting on non-numeric, non-integer, or negative values. The underlying C implementation passes the offset directly to uv_fs_read, replacing the previous hardcoded zero. Documentation in the io module markdown is updated with usage examples for both signatures, and the old TODO comment about missing offset support is removed. New test files cover offset-based reads, edge cases (zero offset, past-end offset, zero count with offset), and error conditions for invalid offset arguments.
1.9 KiB
^title File Class
Lets you work with files on the file system. An instance of this class represents an open file with a file descriptor.
When you are done with a file object, it's a good idea to explicitly close it. If you don't, the GC will close it when the file is no longer used and gets finalized, but that may take a while. In the meantime, leaving it open wastes a file descriptor.
Static Methods
File.open(path, fn)
Opens the file at path and passes it to fn. After the function returns, the
file is automatically closed.
:::wren
File.open("words.txt") {|file|
file.readBytes(5)
}
File.read(path)
Reads the entire contents of the file at path and returns it as a string.
:::wren
File.read("words.txt")
The encoding or decoding is done. If the file is UTF-8, then the resulting string will be a UTF-8 string. Otherwise, it will be a string of bytes in whatever encoding the file uses.
File.size(path)
Returns the size in bytes of the contents of the file at path.
Constructors
File.open(path)
Opens the file at path for reading.
Methods
descriptor
The numeric file descriptor used to access the file.
isOpen
Whether the file is still open or has been closed.
size
The size of the contents of the file in bytes.
close()
Closes the file. After calling this, you can read or write from it.
readBytes(count)
Reads up to count bytes starting from the beginning of the file.
:::wren
// Assume this file contains "I am a file!".
File.open("example.txt") {|file|
System.print(file.readBytes(6)) //> I am a
}
readBytes(count, offset)
Reads up to count bytes starting at offset bytes from the beginning of
the file.
:::wren
// Assume this file contains "I am a file!".
File.open("example.txt") {|file|
System.print(file.readBytes(6, 2)) //> am a f
}