Mojo struct
FileHandle
struct FileHandle
File handle to an opened file.
Fields
- handle (
UnsafePointer[NoneType]): The underlying pointer to the file handle.
Implemented traits
AnyType,
UnknownDestructibility,
Writer
Methods
__init__
__init__(out self)
Default constructor.
__init__(out self, path: StringSlice[origin], mode: StringSlice[origin])
Construct the FileHandle using the file path and mode.
Args:
- path (
StringSlice[origin]): The file path. - mode (
StringSlice[origin]): The mode to open the file in (the mode can be "r" or "w" or "rw").
__moveinit__
__moveinit__(out self, owned existing: Self)
Moves constructor for the file handle.
Args:
- existing (
Self): The existing file handle.
__del__
__del__(owned self)
Closes the file handle.
close
close(mut self)
Closes the file handle.
read
read(self, size: SIMD[int64, 1] = __init__[__mlir_type.!pop.int_literal](-1)) -> String
Reads data from a file and sets the file handle seek position. If size is left as the default of -1, it will read to the end of the file. Setting size to a number larger than what's in the file will set the String length to the total number of bytes, and read all the data.
Examples:
Read the entire file into a String:
var file = open("/tmp/example.txt", "r")
var string = file.read()
print(string)
var file = open("/tmp/example.txt", "r")
var string = file.read()
print(string)
Read the first 8 bytes, skip 2 bytes, and then read the next 8 bytes:
import os
var file = open("/tmp/example.txt", "r")
var word1 = file.read(8)
print(word1)
_ = file.seek(2, os.SEEK_CUR)
var word2 = file.read(8)
print(word2)
import os
var file = open("/tmp/example.txt", "r")
var word1 = file.read(8)
print(word1)
_ = file.seek(2, os.SEEK_CUR)
var word2 = file.read(8)
print(word2)
Read the last 8 bytes in the file, then the first 8 bytes
_ = file.seek(-8, os.SEEK_END)
var last_word = file.read(8)
print(last_word)
_ = file.seek(8, os.SEEK_SET) # os.SEEK_SET is the default start of file
var first_word = file.read(8)
print(first_word)
_ = file.seek(-8, os.SEEK_END)
var last_word = file.read(8)
print(last_word)
_ = file.seek(8, os.SEEK_SET) # os.SEEK_SET is the default start of file
var first_word = file.read(8)
print(first_word)
.
Args:
- size (
SIMD[int64, 1]): Requested number of bytes to read (Default: -1 = EOF).
Returns:
The contents of the file.
Raises:
An error if this file handle is invalid, or if the file read returned a failure.
read[dtype: DType](self, ptr: UnsafePointer[SIMD[dtype, 1]], size: SIMD[int64, 1] = __init__[__mlir_type.!pop.int_literal](-1)) -> SIMD[int64, 1]
Read data from the file into the pointer. Setting size will read up to sizeof(type) * size. The default value of size is -1 which will read to the end of the file. Starts reading from the file handle seek pointer, and after reading adds sizeof(type) * size bytes to the seek pointer.
Examples:
import os
alias file_name = "/tmp/example.txt"
var file = open(file_name, "r")
# Allocate and load 8 elements
var ptr = UnsafePointer[Float32].alloc(8)
var bytes = file.read(ptr, 8)
print("bytes read", bytes)
var first_element = ptr[0]
print(first_element)
# Skip 2 elements
_ = file.seek(2 * sizeof[DType.float32](), os.SEEK_CUR)
# Allocate and load 8 more elements from file handle seek position
var ptr2 = UnsafePointer[Float32].alloc(8)
var bytes2 = file.read(ptr2, 8)
var eleventh_element = ptr2[0]
var twelvth_element = ptr2[1]
print(eleventh_element, twelvth_element)
# Free the memory
ptr.free()
ptr2.free()
import os
alias file_name = "/tmp/example.txt"
var file = open(file_name, "r")
# Allocate and load 8 elements
var ptr = UnsafePointer[Float32].alloc(8)
var bytes = file.read(ptr, 8)
print("bytes read", bytes)
var first_element = ptr[0]
print(first_element)
# Skip 2 elements
_ = file.seek(2 * sizeof[DType.float32](), os.SEEK_CUR)
# Allocate and load 8 more elements from file handle seek position
var ptr2 = UnsafePointer[Float32].alloc(8)
var bytes2 = file.read(ptr2, 8)
var eleventh_element = ptr2[0]
var twelvth_element = ptr2[1]
print(eleventh_element, twelvth_element)
# Free the memory
ptr.free()
ptr2.free()
.
Parameters:
- dtype (
DType): The type that will the data will be represented as.
Args:
- ptr (
UnsafePointer[SIMD[dtype, 1]]): The pointer where the data will be read to. - size (
SIMD[int64, 1]): Requested number of elements to read.
Returns:
The total amount of data that was read in bytes.
Raises:
An error if this file handle is invalid, or if the file read returned a failure.
read_bytes
read_bytes(self, size: SIMD[int64, 1] = __init__[__mlir_type.!pop.int_literal](-1)) -> List[SIMD[uint8, 1]]
Reads data from a file and sets the file handle seek position. If size is left as default of -1, it will read to the end of the file. Setting size to a number larger than what's in the file will be handled and set the List length to the total number of bytes in the file.
Examples:
Reading the entire file into a List[Int8]:
var file = open("/tmp/example.txt", "r")
var string = file.read_bytes()
var file = open("/tmp/example.txt", "r")
var string = file.read_bytes()
Reading the first 8 bytes, skipping 2 bytes, and then reading the next 8 bytes:
import os
var file = open("/tmp/example.txt", "r")
var list1 = file.read(8)
_ = file.seek(2, os.SEEK_CUR)
var list2 = file.read(8)
import os
var file = open("/tmp/example.txt", "r")
var list1 = file.read(8)
_ = file.seek(2, os.SEEK_CUR)
var list2 = file.read(8)
Reading the last 8 bytes in the file, then the first 8 bytes:
import os
var file = open("/tmp/example.txt", "r")
_ = file.seek(-8, os.SEEK_END)
var last_data = file.read(8)
_ = file.seek(8, os.SEEK_SET) # os.SEEK_SET is the default start of file
var first_data = file.read(8)
import os
var file = open("/tmp/example.txt", "r")
_ = file.seek(-8, os.SEEK_END)
var last_data = file.read(8)
_ = file.seek(8, os.SEEK_SET) # os.SEEK_SET is the default start of file
var first_data = file.read(8)
.
Args:
- size (
SIMD[int64, 1]): Requested number of bytes to read (Default: -1 = EOF).
Returns:
The contents of the file.
Raises:
An error if this file handle is invalid, or if the file read returned a failure.
seek
seek(self, offset: SIMD[uint64, 1], whence: SIMD[uint8, 1] = __init__[__mlir_type.!pop.int_literal](0)) -> SIMD[uint64, 1]
Seeks to the given offset in the file.
Examples:
Skip 32 bytes from the current read position:
import os
var f = open("/tmp/example.txt", "r")
_ = f.seek(32, os.SEEK_CUR)
import os
var f = open("/tmp/example.txt", "r")
_ = f.seek(32, os.SEEK_CUR)
Start from 32 bytes from the end of the file:
import os
var f = open("/tmp/example.txt", "r")
_ = f.seek(-32, os.SEEK_END)
import os
var f = open("/tmp/example.txt", "r")
_ = f.seek(-32, os.SEEK_END)
.
Args:
- offset (
SIMD[uint64, 1]): The byte offset to seek to. - whence (
SIMD[uint8, 1]): The reference point for the offset: os.SEEK_SET = 0: start of file (Default). os.SEEK_CUR = 1: current position. os.SEEK_END = 2: end of file.
Returns:
The resulting byte offset from the start of the file.
Raises:
An error if this file handle is invalid, or if file seek returned a failure.
write_bytes
write_bytes(mut self, bytes: Span[SIMD[uint8, 1], origin])
Write a span of bytes to the file.
Args:
- bytes (
Span[SIMD[uint8, 1], origin]): The byte span to write to this file.
write
write[*Ts: Writable](mut self, *args: *Ts)
Write a sequence of Writable arguments to the provided Writer.
Parameters:
- *Ts (
Writable): Types of the provided argument sequence.
Args:
- *args (
*Ts): Sequence of arguments to write to this Writer.
__enter__
__enter__(owned self) -> Self
The function to call when entering the context.
Returns:
The file handle.
Was this page helpful?
Thank you! We'll create more content like this.
Thank you for helping us improve!