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This module provides a stream interface and two implementations thereof: the FileStream and the StringStream which implement the stream interface for Nim file objects (File) and strings.

Other modules may provide other implementations for this standard stream interface.

Warning: Due to the use of pointer, the readData, peekData and

writeData interfaces are not available on the compile-time VM, and must be cast from a ptr string on the JS backend. However, readDataStr is available generally in place of readData.

Basic usage

The basic flow of using this module is:

Open input stream
Read or write stream
Close stream

StringStream example

import std/streams

var strm = newStringStream("""The first line
the second line
the third line""")

var line = ""

while strm.readLine(line):
  echo line

# Output:
# The first line
# the second line
# the third line

strm.close()

FileStream example

Write file stream example:

import std/streams

var strm = newFileStream("somefile.txt", fmWrite)
var line = ""

if not isNil(strm):
  strm.writeLine("The first line")
  strm.writeLine("the second line")
  strm.writeLine("the third line")
  strm.close()

# Output (somefile.txt):
# The first line
# the second line
# the third line

Read file stream example:

import std/streams

var strm = newFileStream("somefile.txt", fmRead)
var line = ""

if not isNil(strm):
  while strm.readLine(line):
    echo line
  strm.close()

# Output:
# The first line
# the second line
# the third line

Imports

since

Types

FileStream = ref FileStreamObj

A stream that encapsulates a File.

Note: Not available for JS backend.

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FileStreamObj = object of Stream

A file stream object.

Note: Not available for JS backend.

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Stream = ref StreamObj

All procedures of this module use this type. Procedures don't directly use StreamObj. Source Edit

StreamObj = object of RootObj
  closeImpl*: proc (s: Stream) {.nimcall, ...raises: [IOError, OSError],
                                 tags: [WriteIOEffect], gcsafe.}
  atEndImpl*: proc (s: Stream): bool {.nimcall,
                                       ...raises: [Defect, IOError, OSError],
                                       tags: [], gcsafe.}
  setPositionImpl*: proc (s: Stream; pos: int) {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [], gcsafe.}
  getPositionImpl*: proc (s: Stream): int {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [], gcsafe.}
  readDataStrImpl*: proc (s: Stream; buffer: var string; slice: Slice[int]): int {.
      nimcall, ...raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
  readLineImpl*: proc (s: Stream; line: var string): bool {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
  readDataImpl*: proc (s: Stream; buffer: pointer; bufLen: int): int {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
  peekDataImpl*: proc (s: Stream; buffer: pointer; bufLen: int): int {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
  writeDataImpl*: proc (s: Stream; buffer: pointer; bufLen: int) {.nimcall,
      ...raises: [Defect, IOError, OSError], tags: [WriteIOEffect], gcsafe.}
  flushImpl*: proc (s: Stream) {.nimcall, ...raises: [Defect, IOError, OSError],
                                 tags: [WriteIOEffect], gcsafe.}

Stream interface that supports writing or reading.

Note:

That these fields here shouldn't be used directly. They are accessible so that a stream implementation can override them.

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StringStream = ref StringStreamObj

A stream that encapsulates a string. Source Edit

StringStreamObj = object of StreamObj
  data*: string              ## A string data.
                             ## This is updated when called `writeLine` etc.

A string stream object. Source Edit

Procs

proc atEnd(s: Stream): bool {....raises: [IOError, OSError], tags: [], forbids: [].}: Checks if more data can be read from s. Returns true if all data has been read.
Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") var line = "" doAssert strm.atEnd() == false while strm.readLine(line): discard doAssert strm.atEnd() == true strm.close()
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proc close(s: Stream) {....raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Closes the stream s.

See also:

flush proc

Example:

block: let strm = newStringStream("The first line\nthe second line\nthe third line") ## do something... strm.close() block: let strm = newFileStream("amissingfile.txt") # deferring works even if newFileStream fails defer: strm.close() if not isNil(strm): ## do something...
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proc flush(s: Stream) {....raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Flushes the buffers that the stream s might use.

This procedure causes any unwritten data for that stream to be delivered to the host environment to be written to the file.

See also:

close proc

Example:

from std/os import removeFile var strm = newFileStream("somefile.txt", fmWrite) doAssert "Before write:" & readFile("somefile.txt") == "Before write:" strm.write("hello") doAssert "After write:" & readFile("somefile.txt") == "After write:" strm.flush() doAssert "After flush:" & readFile("somefile.txt") == "After flush:hello" strm.write("HELLO") strm.flush() doAssert "After flush:" & readFile("somefile.txt") == "After flush:helloHELLO" strm.close() doAssert "After close:" & readFile("somefile.txt") == "After close:helloHELLO" removeFile("somefile.txt")
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proc getPosition(s: Stream): int {....raises: [IOError, OSError], tags: [], forbids: [].}: Retrieves the current position in the stream s.
Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") doAssert strm.getPosition() == 0 discard strm.readLine() doAssert strm.getPosition() == 15 strm.close()
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proc newFileStream(f: File): owned FileStream {....raises: [], tags: [], forbids: [].}: Creates a new stream from the file f.

Note: Not available for JS backend.

See also:

newStringStream proc creates a new stream from string.

newFileStream proc is the same as using open proc on Examples.

openFileStream proc creates a file stream from the file name and the mode.

Example:

## Input (somefile.txt): ## The first line ## the second line ## the third line var f: File if open(f, "somefile.txt", fmRead, -1): var strm = newFileStream(f) var line = "" while strm.readLine(line): echo line ## Output: ## The first line ## the second line ## the third line strm.close()
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proc newFileStream(filename: string; mode: FileMode = fmRead; bufSize: int = -1): owned FileStream {....raises: [], tags: [], forbids: [].}: Creates a new stream from the file named filename with the mode mode.

If the file cannot be opened, nil is returned. See the io module for a list of available FileMode enums.

Note:

This function returns nil in case of failure. To prevent unexpected behavior and ensure proper error handling, use openFileStream proc instead.

Not available for JS backend.

See also:

newStringStream proc creates a new stream from string.

newFileStream proc creates a file stream from opened File.

openFileStream proc creates a file stream from the file name and the mode.

Example:

from std/os import removeFile var strm = newFileStream("somefile.txt", fmWrite) if not isNil(strm): strm.writeLine("The first line") strm.writeLine("the second line") strm.writeLine("the third line") strm.close() ## Output (somefile.txt) ## The first line ## the second line ## the third line removeFile("somefile.txt")
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proc newStringStream(s: sink string = ""): owned StringStream {....raises: [], tags: [], forbids: [].}: Creates a new stream from the string s.

See also:

newFileStream proc creates a file stream from opened File.

newFileStream proc creates a file stream from the file name and the mode.

openFileStream proc creates a file stream from the file name and the mode.

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") doAssert strm.readLine() == "The first line" doAssert strm.readLine() == "the second line" doAssert strm.readLine() == "the third line" strm.close()
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proc openFileStream(filename: string; mode: FileMode = fmRead; bufSize: int = -1): owned FileStream {....raises: [IOError], tags: [], forbids: [].}: Creates a new stream from the file named filename with the mode mode. If the file cannot be opened, an IO exception is raised.

Note: Not available for JS backend.

See also:

newStringStream proc creates a new stream from string.

newFileStream proc creates a file stream from opened File.

newFileStream proc creates a file stream from the file name and the mode.

Example:

try: ## Input (somefile.txt): ## The first line ## the second line ## the third line var strm = openFileStream("somefile.txt") echo strm.readLine() ## Output: ## The first line strm.close() except: stderr.write getCurrentExceptionMsg()
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proc peek[T](s: Stream; result: var T): Generic peek procedure. Peeks result from the stream s.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream("012") ## peekInt var i: int8 strm.peek(i) doAssert i == 48 ## peekData var buffer: array[2, char] strm.peek(buffer) doAssert buffer == ['0', '1'] strm.close()
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proc peekBool(s: Stream): bool {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a bool from the stream s.

A bool is one byte long and it is true for every non-zero (0000_0000) value. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(true) strm.write(false) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekBool() == true ## not false doAssert strm.peekBool() == true doAssert strm.readBool() == true doAssert strm.peekBool() == false strm.close()
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proc peekChar(s: Stream): char {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a char from the stream s. Raises IOError if an error occurred. Returns '\0' as an EOF marker.
Example:

var strm = newStringStream("12\n3") doAssert strm.peekChar() == '1' doAssert strm.peekChar() == '1' discard strm.readAll() doAssert strm.peekChar() == '\x00' strm.close()
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proc peekData(s: Stream; buffer: pointer; bufLen: int): int {. ...raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Low level proc that reads data into an untyped buffer of bufLen size without moving stream position.

JS note: buffer is treated as a ptr string and written to between 0..<bufLen.

Example:

var strm = newStringStream("abcde") var buffer: array[6, char] doAssert strm.peekData(addr(buffer), 1024) == 5 doAssert buffer == ['a', 'b', 'c', 'd', 'e', '\x00'] doAssert strm.atEnd() == false strm.close()
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proc peekFloat32(s: Stream): float32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a float32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'f32) strm.write(2'f32) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekFloat32() == 1'f32 ## not 2'f32 doAssert strm.peekFloat32() == 1'f32 doAssert strm.readFloat32() == 1'f32 doAssert strm.peekFloat32() == 2'f32 strm.close()
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proc peekFloat64(s: Stream): float64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a float64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'f64) strm.write(2'f64) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekFloat64() == 1'f64 ## not 2'f64 doAssert strm.peekFloat64() == 1'f64 doAssert strm.readFloat64() == 1'f64 doAssert strm.peekFloat64() == 2'f64 strm.close()
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proc peekInt8(s: Stream): int8 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an int8 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i8) strm.write(2'i8) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekInt8() == 1'i8 ## not 2'i8 doAssert strm.peekInt8() == 1'i8 doAssert strm.readInt8() == 1'i8 doAssert strm.peekInt8() == 2'i8 strm.close()
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proc peekInt16(s: Stream): int16 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an int16 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i16) strm.write(2'i16) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekInt16() == 1'i16 ## not 2'i16 doAssert strm.peekInt16() == 1'i16 doAssert strm.readInt16() == 1'i16 doAssert strm.peekInt16() == 2'i16 strm.close()
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proc peekInt32(s: Stream): int32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an int32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i32) strm.write(2'i32) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekInt32() == 1'i32 ## not 2'i32 doAssert strm.peekInt32() == 1'i32 doAssert strm.readInt32() == 1'i32 doAssert strm.peekInt32() == 2'i32 strm.close()
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proc peekInt64(s: Stream): int64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an int64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i64) strm.write(2'i64) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekInt64() == 1'i64 ## not 2'i64 doAssert strm.peekInt64() == 1'i64 doAssert strm.readInt64() == 1'i64 doAssert strm.peekInt64() == 2'i64 strm.close()
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proc peekLine(s: Stream): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a line from a stream s. Raises IOError if an error occurred.

Note: This is not very efficient.

See also:

readLine(Stream) proc

readLine(Stream, string) proc

peekLine(Stream, string) proc

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") doAssert strm.peekLine() == "The first line" ## not "the second line" doAssert strm.peekLine() == "The first line" doAssert strm.readLine() == "The first line" doAssert strm.peekLine() == "the second line" strm.close()
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proc peekLine(s: Stream; line: var string): bool {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a line of text from the stream s into line. line must not be nil! May throw an IO exception.

A line of text may be delimited by CR, LF or CRLF. The newline character(s) are not part of the returned string. Returns false if the end of the file has been reached, true otherwise. If false is returned line contains no new data.

See also:

readLine(Stream) proc

readLine(Stream, string) proc

peekLine(Stream) proc

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") var line = "" doAssert strm.peekLine(line) == true doAssert line == "The first line" doAssert strm.peekLine(line) == true ## not "the second line" doAssert line == "The first line" doAssert strm.readLine(line) == true doAssert line == "The first line" doAssert strm.peekLine(line) == true doAssert line == "the second line" strm.close()
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proc peekStr(s: Stream; length: int): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a string of length length from the stream s. Raises IOError if an error occurred.
Example:

var strm = newStringStream("abcde") doAssert strm.peekStr(2) == "ab" ## not "cd doAssert strm.peekStr(2) == "ab" doAssert strm.readStr(2) == "ab" doAssert strm.peekStr(2) == "cd" strm.close()
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proc peekStr(s: Stream; length: int; str: var string) {. ...raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks a string of length length from the stream s. Raises IOError if an error occurred. Source Edit
proc peekUint8(s: Stream): uint8 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an uint8 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u8) strm.write(2'u8) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekUint8() == 1'u8 ## not 2'u8 doAssert strm.peekUint8() == 1'u8 doAssert strm.readUint8() == 1'u8 doAssert strm.peekUint8() == 2'u8 strm.close()
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proc peekUint16(s: Stream): uint16 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an uint16 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u16) strm.write(2'u16) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekUint16() == 1'u16 ## not 2'u16 doAssert strm.peekUint16() == 1'u16 doAssert strm.readUint16() == 1'u16 doAssert strm.peekUint16() == 2'u16 strm.close()
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proc peekUint32(s: Stream): uint32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an uint32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u32) strm.write(2'u32) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekUint32() == 1'u32 ## not 2'u32 doAssert strm.peekUint32() == 1'u32 doAssert strm.readUint32() == 1'u32 doAssert strm.peekUint32() == 2'u32 strm.close()
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proc peekUint64(s: Stream): uint64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Peeks an uint64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use peekStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u64) strm.write(2'u64) strm.flush() strm.setPosition(0) ## get data doAssert strm.peekUint64() == 1'u64 ## not 2'u64 doAssert strm.peekUint64() == 1'u64 doAssert strm.readUint64() == 1'u64 doAssert strm.peekUint64() == 2'u64 strm.close()
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proc read[T](s: Stream; result: var T): Generic read procedure. Reads result from the stream s.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream("012") ## readInt var i: int8 strm.read(i) doAssert i == 48 ## readData var buffer: array[2, char] strm.read(buffer) doAssert buffer == ['1', '2'] strm.close()
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proc readAll(s: Stream): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads all available data.
Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") doAssert strm.readAll() == "The first line\nthe second line\nthe third line" doAssert strm.atEnd() == true strm.close()
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proc readBool(s: Stream): bool {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a bool from the stream s.

A bool is one byte long and it is true for every non-zero (0000_0000) value. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(true) strm.write(false) strm.flush() strm.setPosition(0) ## get data doAssert strm.readBool() == true doAssert strm.readBool() == false doAssertRaises(IOError): discard strm.readBool() strm.close()
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proc readChar(s: Stream): char {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a char from the stream s.

Raises IOError if an error occurred. Returns '\0' as an EOF marker.

Example:

var strm = newStringStream("12\n3") doAssert strm.readChar() == '1' doAssert strm.readChar() == '2' doAssert strm.readChar() == '\n' doAssert strm.readChar() == '3' doAssert strm.readChar() == '\x00' strm.close()
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proc readData(s: Stream; buffer: pointer; bufLen: int): int {. ...raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Low level proc that reads data into an untyped buffer of bufLen size.

JS note: buffer is treated as a ptr string and written to between 0..<bufLen.

Example:

var strm = newStringStream("abcde") var buffer: array[6, char] doAssert strm.readData(addr(buffer), 1024) == 5 doAssert buffer == ['a', 'b', 'c', 'd', 'e', '\x00'] doAssert strm.atEnd() == true strm.close()
Source Edit
proc readDataStr(s: Stream; buffer: var string; slice: Slice[int]): int {. ...raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Low level proc that reads data into a string buffer at slice.
Example:

var strm = newStringStream("abcde") var buffer = "12345" doAssert strm.readDataStr(buffer, 0..3) == 4 doAssert buffer == "abcd5" strm.close()
Source Edit
proc readFloat32(s: Stream): float32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a float32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'f32) strm.write(2'f32) strm.flush() strm.setPosition(0) ## get data doAssert strm.readFloat32() == 1'f32 doAssert strm.readFloat32() == 2'f32 doAssertRaises(IOError): discard strm.readFloat32() strm.close()
Source Edit
proc readFloat64(s: Stream): float64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a float64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'f64) strm.write(2'f64) strm.flush() strm.setPosition(0) ## get data doAssert strm.readFloat64() == 1'f64 doAssert strm.readFloat64() == 2'f64 doAssertRaises(IOError): discard strm.readFloat64() strm.close()
Source Edit
proc readInt8(s: Stream): int8 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an int8 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i8) strm.write(2'i8) strm.flush() strm.setPosition(0) ## get data doAssert strm.readInt8() == 1'i8 doAssert strm.readInt8() == 2'i8 doAssertRaises(IOError): discard strm.readInt8() strm.close()
Source Edit
proc readInt16(s: Stream): int16 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an int16 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i16) strm.write(2'i16) strm.flush() strm.setPosition(0) ## get data doAssert strm.readInt16() == 1'i16 doAssert strm.readInt16() == 2'i16 doAssertRaises(IOError): discard strm.readInt16() strm.close()
Source Edit
proc readInt32(s: Stream): int32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an int32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i32) strm.write(2'i32) strm.flush() strm.setPosition(0) ## get data doAssert strm.readInt32() == 1'i32 doAssert strm.readInt32() == 2'i32 doAssertRaises(IOError): discard strm.readInt32() strm.close()
Source Edit
proc readInt64(s: Stream): int64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an int64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'i64) strm.write(2'i64) strm.flush() strm.setPosition(0) ## get data doAssert strm.readInt64() == 1'i64 doAssert strm.readInt64() == 2'i64 doAssertRaises(IOError): discard strm.readInt64() strm.close()
Source Edit
proc readLine(s: Stream): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a line from a stream s. Raises IOError if an error occurred.

Note: This is not very efficient.

See also:

readLine(Stream, string) proc

peekLine(Stream) proc

peekLine(Stream, string) proc

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") doAssert strm.readLine() == "The first line" doAssert strm.readLine() == "the second line" doAssert strm.readLine() == "the third line" doAssertRaises(IOError): discard strm.readLine() strm.close()
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proc readLine(s: Stream; line: var string): bool {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a line of text from the stream s into line. line must not be nil! May throw an IO exception.

A line of text may be delimited by LF or CRLF. The newline character(s) are not part of the returned string. Returns false if the end of the file has been reached, true otherwise. If false is returned line contains no new data.

See also:

readLine(Stream) proc

peekLine(Stream) proc

peekLine(Stream, string) proc

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") var line = "" doAssert strm.readLine(line) == true doAssert line == "The first line" doAssert strm.readLine(line) == true doAssert line == "the second line" doAssert strm.readLine(line) == true doAssert line == "the third line" doAssert strm.readLine(line) == false doAssert line == "" strm.close()
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proc readStr(s: Stream; length: int): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a string of length length from the stream s. Raises IOError if an error occurred.
Example:

var strm = newStringStream("abcde") doAssert strm.readStr(2) == "ab" doAssert strm.readStr(2) == "cd" doAssert strm.readStr(2) == "e" doAssert strm.readStr(2) == "" strm.close()
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proc readStr(s: Stream; length: int; str: var string) {. ...raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads a string of length length from the stream s. Raises IOError if an error occurred. Source Edit
proc readUint8(s: Stream): uint8 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an uint8 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u8) strm.write(2'u8) strm.flush() strm.setPosition(0) ## get data doAssert strm.readUint8() == 1'u8 doAssert strm.readUint8() == 2'u8 doAssertRaises(IOError): discard strm.readUint8() strm.close()
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proc readUint16(s: Stream): uint16 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an uint16 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u16) strm.write(2'u16) strm.flush() strm.setPosition(0) ## get data doAssert strm.readUint16() == 1'u16 doAssert strm.readUint16() == 2'u16 doAssertRaises(IOError): discard strm.readUint16() strm.close()
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proc readUint32(s: Stream): uint32 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an uint32 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u32) strm.write(2'u32) strm.flush() strm.setPosition(0) ## get data doAssert strm.readUint32() == 1'u32 doAssert strm.readUint32() == 2'u32 doAssertRaises(IOError): discard strm.readUint32() strm.close()
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proc readUint64(s: Stream): uint64 {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Reads an uint64 from the stream s. Raises IOError if an error occurred.

Note: Not available for JS backend. Use readStr for now.

Example:

var strm = newStringStream() ## setup for reading data strm.write(1'u64) strm.write(2'u64) strm.flush() strm.setPosition(0) ## get data doAssert strm.readUint64() == 1'u64 doAssert strm.readUint64() == 2'u64 doAssertRaises(IOError): discard strm.readUint64() strm.close()
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proc setPosition(s: Stream; pos: int) {....raises: [IOError, OSError], tags: [], forbids: [].}: Sets the position pos of the stream s.
Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") strm.setPosition(4) doAssert strm.readLine() == "first line" strm.setPosition(0) doAssert strm.readLine() == "The first line" strm.close()
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proc write(s: Stream; args: varargs[string, `$`]) {....raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Writes one or more strings to the the stream. No length fields or terminating zeros are written.
Example:

var strm = newStringStream("") strm.write(1, 2, 3, 4) strm.setPosition(0) doAssert strm.readLine() == "1234" strm.close()
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proc write(s: Stream; x: string) {....raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Writes the string x to the stream s. No length field or terminating zero is written.
Example:

var strm = newStringStream("") strm.write("THE FIRST LINE") strm.setPosition(0) doAssert strm.readLine() == "THE FIRST LINE" strm.close()
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proc write[T](s: Stream; x: T): Generic write procedure. Writes x to the stream s. Implementation:

Note: Not available for JS backend. Use write(Stream, string) for now.

s.writeData(s, unsafeAddr(x), sizeof(x))

Example:

var strm = newStringStream("") strm.write("abcde") strm.setPosition(0) doAssert strm.readAll() == "abcde" strm.close()
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proc writeData(s: Stream; buffer: pointer; bufLen: int) {. ...raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Low level proc that writes an untyped buffer of bufLen size to the stream s.

JS note: buffer is treated as a ptr string and read between 0..<bufLen.

Example:

## writeData var strm = newStringStream("") var buffer = ['a', 'b', 'c', 'd', 'e'] strm.writeData(addr(buffer), sizeof(buffer)) doAssert strm.atEnd() == true ## readData strm.setPosition(0) var buffer2: array[6, char] doAssert strm.readData(addr(buffer2), sizeof(buffer2)) == 5 doAssert buffer2 == ['a', 'b', 'c', 'd', 'e', '\x00'] strm.close()
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proc writeLine(s: Stream; args: varargs[string, `$`]) {. ...raises: [IOError, OSError], tags: [WriteIOEffect], forbids: [].}: Writes one or more strings to the the stream s followed by a new line. No length field or terminating zero is written.
Example:

var strm = newStringStream("") strm.writeLine(1, 2) strm.writeLine(3, 4) strm.setPosition(0) doAssert strm.readAll() == "12\n34\n" strm.close()
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Iterators

iterator lines(s: Stream): string {....raises: [IOError, OSError], tags: [ReadIOEffect], forbids: [].}: Iterates over every line in the stream. The iteration is based on readLine.

See also:

readLine(Stream) proc

readLine(Stream, string) proc

Example:

var strm = newStringStream("The first line\nthe second line\nthe third line") var lines: seq[string] for line in strm.lines(): lines.add line doAssert lines == @["The first line", "the second line", "the third line"] strm.close()
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