io

package
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 Go to latest Published: Apr 13, 2026 License: Apache-2.0 Imports: 16 Imported by: 0

Documentation

Overview

Package io provides I/O primitives for reading and writing.

Textual Read (R7RS 6.13.2)

  • read, read-char, peek-char, char-ready?, read-line, read-string
  • read-syntax, read-token

Textual Write (R7RS 6.13.3)

  • write, display, newline, write-char, write-string
  • write-simple, write-shared
  • flush-output-port

Binary I/O

  • read-u8, peek-u8, u8-ready?, write-u8
  • read-bytevector, read-bytevector!, write-bytevector

Port Predicates

  • port?, input-port?, output-port?
  • textual-port?, binary-port?
  • input-port-open?, output-port-open?
  • eof-object, eof-object?

String and Bytevector Ports

  • open-input-string, open-output-string, get-output-string
  • open-input-bytevector, open-output-bytevector, get-output-bytevector

Port State

  • current-input-port, current-output-port, current-error-port
  • close-port, close-input-port, close-output-port
  • call-with-port

Use Extension or AddToRegistry to register all primitives.

Package io provides I/O primitives for reading and writing.

Index

Constants

View Source 
const (
	// MaxReadBytevectorBytes is the maximum size of bytevector that
	// read-bytevector can allocate (100 MB).
	MaxReadBytevectorBytes = 100 * 1024 * 1024 // 100 MB
)
View Source 
const (
	// MaxReadStringBytes is the maximum memory that read-string can allocate
	// for the character buffer (100 MB). Assumes 4 bytes per rune (worst case).
	MaxReadStringBytes = 100 * 1024 * 1024 // 100 MB
)

Variables

View Source 
var (

	// Tokenizers caches tokenizers per input port.
	//
	// Entries are evicted via evictPortCache() on port close or EOF.
	// Ports that are abandoned without close or EOF will retain their
	// cache entries until the process exits. If that becomes a problem
	// in long-running programs, switch to weak.Pointer[T] (Go 1.24+).
	//
	// Thread safety: All access must be protected by cacheMu.
	Tokenizers map[values.Value]*tokenizer.Tokenizer
	// Parsers caches parsers per input port.
	// Same retention caveat as Tokenizers above.
	//
	// Thread safety: All access must be protected by cacheMu.
	Parsers map[values.Value]*parser.Parser
	// ProgramStartTime is used for current-jiffy to measure elapsed time.
	ProgramStartTime = time.Now()
)

Package-level state for I/O ports. These are lazily initialized on first access.

View Source 
var AddToRegistry = Builder.AddToRegistry

AddToRegistry registers all I/O primitives.

View Source 
var Builder = registry.NewRegistryBuilder(
	addReadWrite,
	addPorts,
	addPortState,
	addPortProcs,
)

Builder aggregates all I/O registration functions.

View Source 
var Extension = registry.NewDescribedExtension("io",
	"I/O ports: reading, writing, string/bytevector ports, display, write.",
	AddToRegistry)

Extension is the I/O extension.

View Source 
var PrimInputPortQ = helpers.MakeTypePredicate(func(o values.Value) bool {
	_, ok := o.(values.InputPort)
	return ok
})
View Source 
var PrimOutputPortQ = helpers.MakeTypePredicate(func(o values.Value) bool {
	_, ok := o.(values.OutputPort)
	return ok
})
View Source 
var PrimPortQ = helpers.MakeTypePredicate(func(o values.Value) bool {
	_, ok := o.(values.Port)
	return ok
})

Port type predicates — R7RS §6.13.1.

Functions

func GetCurrentErrorPortParam 

func GetCurrentErrorPortParam() *machine.Parameter

GetCurrentErrorPortParam returns the current-error-port parameter object.

func GetCurrentInputPort 

func GetCurrentInputPort() values.TextualReader

GetCurrentInputPort returns the base input port from the parameter. This is a test convenience for save/restore; production code should use resolveCurrentInputPort which checks continuation marks from parameterize.

func GetCurrentInputPortParam 

func GetCurrentInputPortParam() *machine.Parameter

GetCurrentInputPortParam returns the current-input-port parameter object.

func GetCurrentOutputPort 

func GetCurrentOutputPort() values.OutputPort

GetCurrentOutputPort returns the base output port from the parameter. This is a test convenience for save/restore; production code should use resolveCurrentOutputPort which checks continuation marks from parameterize.

func GetCurrentOutputPortParam 

func GetCurrentOutputPortParam() *machine.Parameter

GetCurrentOutputPortParam returns the current-output-port parameter object.

func InitState 

func InitState()

InitState initializes the primitives state. Must be called before using I/O primitives. Safe to call multiple times - subsequent calls are no-ops. Thread-safe: protected by stateMu.

func PrimBinaryPortQ 

func PrimBinaryPortQ(mc machine.CallContext) error

PrimBinaryPortQ implements the binary-port? primitive. R7RS §6.13.1: Returns #t if the port is a binary port, #f otherwise.

func PrimCharReadyQ 

func PrimCharReadyQ(mc machine.CallContext) error

PrimCharReadyQ implements the char-ready? primitive. R7RS §6.13.2: (char-ready? [port]) Returns #t if a character is ready on the input port, #f otherwise.

func PrimCloseInputPort added in v1.5.0 

func PrimCloseInputPort(mc machine.CallContext) error

PrimCloseInputPort implements the (close-input-port) primitive. Requires an input port; errors if given an output port.

R7RS §6.13.1: close-input-port takes an input port.

func PrimCloseOutputPort added in v1.5.0 

func PrimCloseOutputPort(mc machine.CallContext) error

PrimCloseOutputPort implements the (close-output-port) primitive. Requires an output port; errors if given an input port. Flushes buffered data before closing.

R7RS §6.13.1: close-output-port takes an output port.

func PrimClosePort 

func PrimClosePort(mc machine.CallContext) error

PrimClosePort implements the (close-port) primitive. Closes an input or output port.

R7RS §6.13.1: Closes the resource associated with port.

func PrimDisplay 

func PrimDisplay(mc machine.CallContext) error

PrimDisplay implements the (display) primitive. Writes a human-readable representation of an object to an output port. R7RS §6.13.3: display uses datum labels to handle circular and shared structures.

func PrimEofObject 

func PrimEofObject(mc machine.CallContext) error

PrimEofObject implements the (eof-object) primitive. Returns the EOF object.

func PrimEofObjectQ 

func PrimEofObjectQ(mc machine.CallContext) error

PrimEofObjectQ implements the (eof-object?) primitive. Returns #t if the argument is the EOF object.

func PrimFlushOutputPort 

func PrimFlushOutputPort(mc machine.CallContext) error

PrimFlushOutputPort implements the flush-output-port primitive. R7RS §6.13.3: (flush-output-port [port]) Flushes any buffered output to the underlying output device.

func PrimGetOutputBytevector 

func PrimGetOutputBytevector(mc machine.CallContext) error

PrimGetOutputBytevector implements the Scheme get-output-bytevector primitive.

func PrimGetOutputString 

func PrimGetOutputString(mc machine.CallContext) error

PrimGetOutputString implements the Scheme get-output-string primitive.

func PrimInputPortOpenQ 

func PrimInputPortOpenQ(mc machine.CallContext) error

PrimInputPortOpenQ implements the (input-port-open?) primitive. Returns #t if input port is open.

R7RS §6.13.1: Returns #t if port is still open and capable of performing input.

func PrimNewline 

func PrimNewline(mc machine.CallContext) error

PrimNewline implements the newline primitive. Writes a newline character to the output port.

func PrimOpenInputBytevector 

func PrimOpenInputBytevector(mc machine.CallContext) error

PrimOpenInputBytevector implements the Scheme open-input-bytevector primitive.

func PrimOpenInputString 

func PrimOpenInputString(mc machine.CallContext) error

PrimOpenInputString implements the Scheme open-input-string primitive.

func PrimOpenOutputBytevector 

func PrimOpenOutputBytevector(mc machine.CallContext) error

PrimOpenOutputBytevector implements the Scheme open-output-bytevector primitive.

func PrimOpenOutputString 

func PrimOpenOutputString(mc machine.CallContext) error

PrimOpenOutputString implements the Scheme open-output-string primitive.

func PrimOutputPortOpenQ 

func PrimOutputPortOpenQ(mc machine.CallContext) error

PrimOutputPortOpenQ implements the output-port-open? primitive. Returns #t if the output port is open, #f otherwise.

R7RS §6.13.1: Returns #t if port is still open and capable of performing output.

func PrimPeekChar 

func PrimPeekChar(mc machine.CallContext) error

PrimPeekChar implements the peek-char primitive. R7RS §6.13.2: (peek-char [port]) Reads and returns a single character from the input port without consuming it.

func PrimPeekU8 

func PrimPeekU8(mc machine.CallContext) error

PrimPeekU8 implements the peek-u8 primitive. R7RS §6.13.3: (peek-u8 [port]) Like read-u8, but does not consume the byte from the port.

func PrimRead 

func PrimRead(mc machine.CallContext) error

PrimRead implements the (read) primitive. Reads a Scheme datum from port. Reads from the current input port if no port is specified. R7RS §6.13.2: read uses datum labels to handle circular and shared structures.

func PrimReadBytevector 

func PrimReadBytevector(mc machine.CallContext) error

PrimReadBytevector implements the read-bytevector primitive. R7RS §6.13.3: (read-bytevector k [port]) Reads the next k bytes from port into a newly allocated bytevector. Returns eof-object if no bytes are available before end of file.

func PrimReadBytevectorBang 

func PrimReadBytevectorBang(mc machine.CallContext) error

PrimReadBytevectorBang implements the read-bytevector! primitive. R7RS §6.13.3: (read-bytevector! bytevector [port [start [end]]]) Reads bytes from port into an existing bytevector. Returns the number of bytes read, or eof-object if no bytes available.

func PrimReadChar 

func PrimReadChar(mc machine.CallContext) error

PrimReadChar implements the read-char primitive. R7RS §6.13.2: (read-char [port]) Reads and returns a single character from the input port.

func PrimReadLine 

func PrimReadLine(mc machine.CallContext) error

PrimReadLine implements the read-line primitive. R7RS §6.13.2: (read-line [port]) Reads a line of text from the input port, not including the line ending.

func PrimReadString 

func PrimReadString(mc machine.CallContext) error

PrimReadString implements the read-string primitive. R7RS §6.13.2: (read-string k [port]) Reads up to k characters from the input port and returns them as a string.

func PrimReadSyntax 

func PrimReadSyntax(mc machine.CallContext) error

PrimReadSyntax implements the (read-syntax) primitive. Reads datum with source information. Reads from the current input port if no port is specified.

func PrimReadToken 

func PrimReadToken(mc machine.CallContext) error

PrimReadToken implements the (read-token) primitive. Reads a single token from port. Reads from the current input port if no port is specified.

func PrimReadU8 

func PrimReadU8(mc machine.CallContext) error

PrimReadU8 implements the read-u8 primitive. R7RS §6.13.3: (read-u8 [port]) Reads the next byte from the given binary input port and returns it as an exact integer. Returns eof-object at end of file.

func PrimTextualPortQ 

func PrimTextualPortQ(mc machine.CallContext) error

PrimTextualPortQ implements the textual-port? primitive. R7RS §6.13.1: Returns #t if the port is a textual port, #f otherwise.

func PrimU8ReadyQ 

func PrimU8ReadyQ(mc machine.CallContext) error

PrimU8ReadyQ implements the u8-ready? primitive. R7RS §6.13.3: (u8-ready? [port]) Returns #t if a byte is available for reading from the binary input port.

func PrimWrite 

func PrimWrite(mc machine.CallContext) error

PrimWrite implements the write primitive. Writes a machine-readable representation of an object to the current output port or to the specified port. R7RS §6.13.3: write uses datum labels to handle circular and shared structures.

func PrimWriteBytevector 

func PrimWriteBytevector(mc machine.CallContext) error

PrimWriteBytevector implements the write-bytevector primitive. R7RS §6.13.3: (write-bytevector bytevector [port [start [end]]]) Writes the bytes of bytevector to port.

func PrimWriteChar 

func PrimWriteChar(mc machine.CallContext) error

PrimWriteChar implements the write-char primitive. Writes a character to the current output port or to the specified output port.

func PrimWriteShared 

func PrimWriteShared(mc machine.CallContext) error

PrimWriteShared implements the write-shared primitive (R7RS). Writes a machine-readable representation of an object using datum labels (#n= and #n#) for shared and circular structure. R7RS §6.13.3: write-shared always uses datum labels for shared structure.

(write-shared obj) or (write-shared obj port)

func PrimWriteSimple 

func PrimWriteSimple(mc machine.CallContext) error

PrimWriteSimple implements the write-simple primitive (R7RS). Writes a machine-readable representation of an object without using datum labels for shared or circular structure. This is the same as write for non-circular data. (write-simple obj) or (write-simple obj port)

func PrimWriteString 

func PrimWriteString(mc machine.CallContext) error

PrimWriteString implements the write-string primitive. R7RS §6.13.3: (write-string string [port [start [end]]]) Writes the characters of string (optionally between start and end) to port.

func PrimWriteU8 

func PrimWriteU8(mc machine.CallContext) error

PrimWriteU8 implements the write-u8 primitive. R7RS §6.13.3: (write-u8 byte [port]) Writes byte to the given binary output port and returns an unspecified value.

func ResetCurrentInputPort 

func ResetCurrentInputPort()

ResetCurrentInputPort resets the current input port to stdin. Used for testing.

func ResetCurrentOutputPort 

func ResetCurrentOutputPort()

ResetCurrentOutputPort resets the current output port to stdout. Used for testing.

func ResetState 

func ResetState()

ResetState resets the primitives state. Used for testing. Thread-safe: protected by stateMu and cacheMu.

func SetCurrentInputPort 

func SetCurrentInputPort(port values.TextualReader)

SetCurrentInputPort sets the current input port value. Used for testing.

func SetCurrentOutputPort 

func SetCurrentOutputPort(port values.OutputPort)

SetCurrentOutputPort sets the current output port value. Used for testing and parameterize.

func StringValue 

func StringValue(o values.Value) string

StringValue returns the display representation of a value. Uses String() if available (for human-readable output), otherwise SchemeString().

Types

This section is empty.

Source Files

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