Christopher M. Punches
cafdeefa11
A module's reported version is consumed: a calling module reads it through dpm_module_info_of and decides from it whether to issue a command. Calling dpm_module_execute the module's entire functional surface contradicted that. dpm_module_execute is the only entry through which a module performs work. dpm_module_version and dpm_module_description are what it reports about itself, read at load and served to consumers, and the contract page in the public header now says so.
390 lines
14 KiB
C
390 lines
14 KiB
C
/**
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* @file core.h
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* @brief Public C API for libdpm-core
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*
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* The single entry point for all DPM consumers: the dpm CLI, modules,
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* and external programs (build systems, Dark Horse tooling). All types
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* crossing this boundary are C types; state passes through opaque
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* handles; errors are int codes with per-context detail strings.
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*
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* @copyright Copyright (c) 2026 SILO GROUP LLC
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* @author Chris Punches <chris.punches@silogroup.org>
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*
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* Part of the Dark Horse Linux Package Manager (DPM)
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#ifndef DPM_CORE_H
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#define DPM_CORE_H
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* ------------------------------------------------------------------ */
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/* Export annotation */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Marks the public API visible
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*
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* The library is compiled with hidden default symbol visibility; the
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* functions carrying this are its entire exported surface.
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*/
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#ifndef DPM_API
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#define DPM_API __attribute__((visibility("default")))
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#endif
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/* ------------------------------------------------------------------ */
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/* Opaque handles */
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/* ------------------------------------------------------------------ */
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typedef struct dpm_ctx dpm_ctx;
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typedef struct dpm_module dpm_module;
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typedef struct dpm_cursor dpm_cursor;
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/* ------------------------------------------------------------------ */
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/* Log levels */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Severity levels accepted by dpm_log()
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*
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* A message at a level above the context's configured level is dropped.
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*/
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enum {
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/** Unrecoverable failure. */
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DPM_LOG_FATAL = 0,
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/** Operation failed. */
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DPM_LOG_ERROR = 1,
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/** Operation continued, something was wrong. */
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DPM_LOG_WARN = 2,
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/** Normal reporting; the default level. */
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DPM_LOG_INFO = 3,
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/** Detail for diagnosing behaviour. */
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DPM_LOG_DEBUG = 4
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};
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/* ------------------------------------------------------------------ */
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/* Context configuration overrides */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Overrides for dpm_open()
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*
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* Any field may be left NULL (or -1 for log_level) to accept
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* configuration-file values and built-in defaults. Every field here is
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* exposed as a flag on the dpm binary.
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*/
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typedef struct dpm_open_overrides {
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/** NULL selects /etc/dpm/conf.d/. */
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const char* config_dir;
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/** NULL selects the configured value, then the built-in default. */
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const char* module_path;
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/** NULL selects "/", the target root for package operations. */
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const char* root;
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/** -1 selects the configured value; otherwise a DPM_LOG_* level. */
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int log_level;
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} dpm_open_overrides;
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/* ------------------------------------------------------------------ */
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/* Module information (enumeration results) */
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/* ------------------------------------------------------------------ */
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/**
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* @brief What the library read from a module at load
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*
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* Filled by dpm_module_info_of() and by dpm_cursor_next(). The string
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* pointers remain valid until the context is closed.
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*/
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typedef struct dpm_module_info {
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/** Module name, its filename minus .so. */
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const char* name;
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/** The module's own X.Y.Z. */
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const char* version;
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/** One-line description. */
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const char* description;
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} dpm_module_info;
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/* ------------------------------------------------------------------ */
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/* Context lifecycle */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Creates a libdpm-core context
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*
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* Reads configuration from /etc/dpm/conf.d/ (or the overridden config
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* directory), resolves the module path (override > config > built-in
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* default), and initializes logging per configuration. Performs no
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* module loading. Multiple simultaneous contexts with different roots
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* are legal.
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*
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* @param overrides Optional overrides; NULL accepts configuration
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* values and built-in defaults
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* @return A context handle, or NULL on allocation failure or an
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* unreadable/invalid explicit override (a missing default
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* config directory is not an error)
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*/
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DPM_API dpm_ctx* dpm_open(const dpm_open_overrides* overrides);
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/**
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* @brief Releases a libdpm-core context
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*
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* Unloads every module handle the context issued, closes log targets,
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* and frees all memory owned by the context. All handles and strings
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* obtained through the context are invalid after this call.
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*
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* @param ctx The context to release; NULL is a no-op
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*/
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DPM_API void dpm_close(dpm_ctx* ctx);
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/* ------------------------------------------------------------------ */
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/* Module acquisition */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Loads and returns a validated module
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*
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* Resolves the named module in the module path and runs the full
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* load-time validation sequence if it is not already loaded in this
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* context. Modules are loaded at most once per context; repeated
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* calls return the same handle.
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*
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* Version compatibility is the caller's judgement: read the loaded
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* module's version with dpm_module_info_of() and decide whether it is
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* acceptable.
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*
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* @param ctx The libdpm-core context
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* @param name The module name (its filename minus .so)
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* @return A module handle owned by the context, or NULL on failure
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* with the precise reason retrievable via dpm_last_error()
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*/
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DPM_API dpm_module* dpm_require(dpm_ctx* ctx, const char* name);
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/**
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* @brief Reports what the library sees in a loaded module
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*
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* Fills `out` with the module's name, version, and description,
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* exactly as they were read at load. The caller decides whether the
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* version it is looking at suits its purposes.
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*
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* @param ctx The libdpm-core context
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* @param mod A module handle from dpm_require()
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* @param out Receives the module's information; the string pointers
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* remain valid until context close
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* @return 0 on success, nonzero if the module cannot be reported on
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*/
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DPM_API int dpm_module_info_of(dpm_ctx* ctx, dpm_module* mod,
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dpm_module_info* out);
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/**
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* @brief Dispatches a command to a module
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*
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* Invokes the module's dpm_module_execute with the context, the
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* command, and the argument vector. argv[0] is the command when
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* argc > 0; semantics beyond that are the module's to define.
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*
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* This is the only path into module code. A caller addresses a module
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* by name and a capability by command string, so it holds no
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* compile-time knowledge of the module it is calling — the same call
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* a module makes to reach a peer.
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*
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* @param ctx The libdpm-core context
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* @param mod A module handle from dpm_require()
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* @param command The command name; NULL or empty behaves as the
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* module's help command
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* @param argc Number of arguments
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* @param argv Argument vector
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* @return The module's return value verbatim; 0 on success
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*/
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DPM_API int dpm_execute(dpm_ctx* ctx, dpm_module* mod, const char* command,
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int argc, char** argv);
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/* ------------------------------------------------------------------ */
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/* Enumeration */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Enumerates the valid modules in the module path
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*
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* Scans the module path and validates each candidate .so; failures
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* are logged and excluded from the results.
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*
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* @param ctx The libdpm-core context
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* @return A cursor over all valid modules, or NULL on an unreadable
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* module path
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*/
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DPM_API dpm_cursor* dpm_list_modules(dpm_ctx* ctx);
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/**
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* @brief Advances an enumeration cursor
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*
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* Fills `out` with the next module's name, version, and description;
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* the string pointers remain valid until context close.
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*
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* @param cur The cursor from dpm_list_modules()
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* @param out Receives the next module's information
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* @return 0 while entries remain; nonzero at end
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*/
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DPM_API int dpm_cursor_next(dpm_cursor* cur, dpm_module_info* out);
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/**
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* @brief Releases an enumeration cursor
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*
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* @param cur The cursor to release; NULL is a no-op
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*/
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DPM_API void dpm_cursor_free(dpm_cursor* cur);
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/* ------------------------------------------------------------------ */
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/* Services (available to modules and external consumers alike) */
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/* ------------------------------------------------------------------ */
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/**
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* @brief Returns libdpm-core's own version
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*
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* @return The libdpm-core version as a static X.Y.Z string; callable
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* without a context
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*/
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DPM_API const char* dpm_core_version(void);
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/**
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* @brief Returns a configuration value from a module's namespace
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*
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* A module's configuration namespace is its own .conf file under the
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* context's configuration directory; the namespace named "core", from
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* core.conf, is the library's own.
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*
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* @param ctx The libdpm-core context
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* @param module The configuration namespace to read
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* @param section The section name within the file
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* @param key The key within the section
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* @return The configured value, or NULL if unset; valid until
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* context close
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*/
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DPM_API const char* dpm_config_get(dpm_ctx* ctx, const char* module,
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const char* section, const char* key);
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/**
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* @brief Writes a message to the context's configured log targets
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*
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* Targets are the console and, when configured, the log file.
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* Messages above the configured level are dropped.
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*
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* @param ctx The libdpm-core context
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* @param level The severity (DPM_LOG_FATAL through DPM_LOG_DEBUG)
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* @param message The message to log; NULL is a no-op
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*/
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DPM_API void dpm_log(dpm_ctx* ctx, int level, const char* message);
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/**
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* @brief Returns the resolved module directory path
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*
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* @param ctx The libdpm-core context
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* @return The module directory path this context resolved
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*/
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DPM_API const char* dpm_module_path(dpm_ctx* ctx);
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/**
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* @brief Returns the most recent failure recorded on the context
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*
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* @param ctx The libdpm-core context
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* @return A human-readable description of the most recent failure, or
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* NULL if none; overwritten by the next failing call
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*/
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DPM_API const char* dpm_last_error(dpm_ctx* ctx);
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/* ------------------------------------------------------------------ */
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/* Module contract (implemented by modules, called by libdpm-core) */
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/* ------------------------------------------------------------------ */
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/**
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* @mainpage libdpm-core.so — API Reference
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*
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* This is the generated reference for libdpm-core.so, extracted from
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* the source. It covers the public C API in <dpm/core.h>, the library's
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* internals, and the module contract.
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*
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* Start at core.h for the API a consumer or a module calls, and at
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* @ref module_contract for what a module implements.
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*
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* The project's prose documentation — overview, design, build, module
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* authoring, and consumer guide — lives in the docs/ directory of the
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* repository and is read there.
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*/
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/**
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* @page module_contract The Module Contract
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*
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* A module is one .so in the module directory. It includes
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* <dpm/core.h>, links -ldpm-core, and exports three reserved symbols as
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* extern "C":
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*
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* @code
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* int dpm_module_execute(dpm_ctx* ctx, const char* command,
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* int argc, char** argv);
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* const char* dpm_module_version(void);
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* const char* dpm_module_description(void);
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* @endcode
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*
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* @section module_contract_surface The Functional Surface
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*
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* dpm_module_execute is the only entry through which a module performs
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* work; its capabilities are addressed by command string, so a module
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* publishes no headers, struct layouts, or symbols to anything that
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* calls it. NULL or an empty command behaves as the module's help
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* command.
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*
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* dpm_module_version and dpm_module_description are what a module
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* reports about itself. The library reads both at load and serves them
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* to consumers through dpm_module_info_of, where the version is what a
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* calling module judges before deciding to issue a command.
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*
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* @section module_contract_version Version Compatibility
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*
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* A module determines for itself whether it can work with the library
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* it is running against: dpm_core_version() reports the running
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* version, and the module proceeds or fails on its own judgement. A
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* module is built against the system-installed libdpm-core.so and is
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* responsible for being correct against it.
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*
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* The same holds toward a peer. A module requires the peer by name,
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* reads the version the library reports, and decides whether that
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* version suits the commands it intends to issue.
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*
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* @section module_contract_validation Validation
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*
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* The library refuses to load any module that does not validate
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* completely: every reserved symbol resolves, and the version and
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* description probes return well-formed values. A module that loads is
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* fully valid.
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*/
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#ifdef __cplusplus
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}
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#endif
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#endif /* DPM_CORE_H */
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