http_range.h

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// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
/**
 * @file http_range.h
 * @brief Shared single-range `Range: bytes=...` parser (RFC 7233), used by static file serving and the
 *        edge cache (DETWS_ENABLE_RANGE).
 *
 * Promoted out of file_serving.cpp so both the filesystem file server and the CDN edge cache share one
 * owner for the range math. Pure and size/string-driven - no DetWebServer or fs:: dependency.
 *
 * @author  Douglas Quigg (dstroy0)
 * @date    2026
 */
 
#ifndef DETERMINISTICESPASYNCWEBSERVER_HTTP_RANGE_H
#define DETERMINISTICESPASYNCWEBSERVER_HTTP_RANGE_H
 
#include "ServerConfig.h"
 
#if DETWS_ENABLE_RANGE
 
#include <stddef.h>
 
/**
 * @brief Parse a single-range `Range: bytes=...` header value against a resource of @p size bytes.
 *
 * Supported forms: "bytes=A-B", "bytes=A-" (A to end), "bytes=-N" (last N bytes). A start past
 * SIZE_MAX saturates (never wraps) so it resolves as past-EOF. @return:
 *   - 0  no usable Range header (caller sends a full 200) - absent, malformed, trailing garbage, or a
 *        multi-range request (RFC 7233 sec 3.1 permits ignoring it),
 *   - 1  a satisfiable range (writes the inclusive [*out_start, *out_end]),
 *   - -1 a syntactically valid but unsatisfiable range (caller sends 416).
 */
int http_parse_byte_range(const char *hdr, size_t size, size_t *out_start, size_t *out_end);
 
#endif // DETWS_ENABLE_RANGE
 
#endif // DETERMINISTICESPASYNCWEBSERVER_HTTP_RANGE_H