object

http_client_core

Portable stream-based HTTP client core predicates.

Availability:

logtalk_load(http_client_core(loader))

Author: Paulo Moura

Version: 1:0:0

Date: 2026-07-08

Compilation flags:

static, context_switching_calls

Imports:

public http_message_helpers

Uses:

http_core

list

Remarks:

• Binary streams: All stream predicates expect binary input and output streams.

• Per-message primitives: The write_request/2, read_response/2, and exchange/4 predicates process a single HTTP exchange.

• Connection sequence: The exchange_sequence/4 predicate performs sequential exchanges on the same stream pair while HTTP persistence rules allow it.

Inherited public predicates:

(none)

Public predicates

write_request/2

Writes exactly one normalized HTTP request term to a binary stream.

Compilation flags:

static

Template:

write_request(Output,Request)

Mode and number of proofs:

write_request(+stream,+compound) - one_or_error

Exceptions:

Request is not a valid normalized HTTP request term:

domain_error(http_request,Request)

The generated request violates normalized HTTP request semantics:

domain_error(http_header_semantics,Header)

The generated request properties violate normalized HTTP request semantics:

domain_error(http_property_semantics,Property)

---

read_response/2

Reads exactly one HTTP response from a binary stream and returns it as a normalized response term. Fails on clean end-of-file before reading any bytes. Responses may be status-bodyless, Content-Length framed, Transfer-Encoding chunked, or close-delimited by end-of-file. Close-delimited responses are annotated with a body_framing(close_delimited) property.

Compilation flags:

static

Template:

read_response(Input,Response)

Mode and number of proofs:

read_response(+stream,--compound) - zero_or_one

Exceptions:

The input stream does not contain a valid normalized HTTP response message:

domain_error(http_response_stream,malformed_response(Bytes))

---

exchange/4

Writes one normalized request to a binary output stream and then reads one normalized response from a binary input stream.

Compilation flags:

static

Template:

exchange(Input,Output,Request,Response)

Mode and number of proofs:

exchange(+stream,+stream,+compound,--compound) - one_or_error

Exceptions:

Request is not a valid normalized HTTP request term:

domain_error(http_request,Request)

The generated request violates normalized HTTP request semantics:

domain_error(http_header_semantics,Header)

The generated request properties violate normalized HTTP request semantics:

domain_error(http_property_semantics,Property)

The input stream ends before a complete response is read:

domain_error(http_response_stream,unexpected_end_of_file)

The input stream does not contain a valid normalized HTTP response status line:

domain_error(http_response_stream,malformed_status_line(Bytes))

The input stream contains an unsupported response transfer encoding:

domain_error(http_response_stream,unsupported_transfer_encoding(Encodings))

The input stream contains an invalid response line ending:

domain_error(http_response_stream,invalid_line_ending(CarriageReturn,LineFeed))

The input stream contains a bare line feed:

domain_error(http_response_stream,bare_line_feed)

The input stream does not contain a valid normalized HTTP response message:

domain_error(http_response_stream,malformed_response(Bytes))

The response declares an invalid content length:

domain_error(non_negative_integer,Length)

---

exchange_sequence/4

Performs a sequence of request-response exchanges on the same binary stream pair. If additional requests remain when HTTP persistence rules require connection closure, an error is thrown.

Compilation flags:

static

Template:

exchange_sequence(Input,Output,Requests,Responses)

Mode and number of proofs:

exchange_sequence(+stream,+stream,++list(compound),--list(compound)) - one_or_error

Exceptions:

Requests is not a valid list of normalized HTTP request terms:

domain_error(http_client_connection,Requests)

A request in Requests is not a valid normalized HTTP request term:

domain_error(http_request,Request)

HTTP persistence requires the connection to close while requests remain to be exchanged:

domain_error(http_client_connection,remaining_requests(Requests))

---

Protected predicates

(no local declarations; see entity ancestors if any)

Private predicates

(no local declarations; see entity ancestors if any)

Operators

(none)