libutil: add C bindings

This commit is contained in:
Yorick van Pelt 2023-07-14 15:52:12 +02:00 committed by José Luis Lafuente
parent c0b6907ccd
commit 4702317506
No known key found for this signature in database
GPG key ID: 8A3455EBE455489A
5 changed files with 437 additions and 1 deletions

View file

@ -2,7 +2,7 @@ GLOBAL_CXXFLAGS += -Wno-deprecated-declarations -Werror=switch
# Allow switch-enum to be overridden for files that do not support it, usually because of dependency headers.
ERROR_SWITCH_ENUM = -Werror=switch-enum
$(foreach i, config.h $(wildcard src/lib*/*.hh), \
$(foreach i, config.h $(wildcard src/lib*/*.hh) $(wildcard src/lib*/*.h), \
$(eval $(call install-file-in, $(i), $(includedir)/nix, 0644)))
$(GCH): src/libutil/util.hh config.h

View file

@ -137,6 +137,10 @@ public:
: err(e)
{ }
std::string message() {
return err.msg.str();
}
const char * what() const noexcept override { return calcWhat().c_str(); }
const std::string & msg() const { return calcWhat(); }
const ErrorInfo & info() const { calcWhat(); return err; }

148
src/libutil/nix_api_util.cc Normal file
View file

@ -0,0 +1,148 @@
#include "nix_api_util.h"
#include "config.hh"
#include "error.hh"
#include "nix_api_util_internal.h"
#include "util.hh"
#include <cxxabi.h>
#include <typeinfo>
nix_c_context *nix_c_context_create() { return new nix_c_context(); }
void nix_c_context_free(nix_c_context *context) { delete context; }
nix_err nix_context_error(nix_c_context *context) {
if (context == nullptr) {
throw;
}
try {
throw;
} catch (nix::Error &e) {
/* Storing this exception is annoying, take what we need here */
context->last_err = e.what();
context->info = e.info();
int status;
const char *demangled =
abi::__cxa_demangle(typeid(e).name(), 0, 0, &status);
if (demangled) {
context->name = demangled;
// todo: free(demangled);
} else {
context->name = typeid(e).name();
}
context->last_err_code = NIX_ERR_NIX_ERROR;
return context->last_err_code;
} catch (const std::exception &e) {
context->last_err = e.what();
context->last_err_code = NIX_ERR_UNKNOWN;
return context->last_err_code;
}
// unreachable
}
nix_err nix_set_err_msg(nix_c_context *context, nix_err err, const char *msg) {
if (context == nullptr) {
// todo last_err_code
throw new nix::Error("Nix C api error", msg);
}
context->last_err_code = err;
context->last_err = msg;
return err;
}
const char *nix_version_get() { return PACKAGE_VERSION; }
// Implementations
nix_err nix_setting_get(nix_c_context *context, const char *key, char *value,
int n) {
if (context)
context->last_err_code = NIX_OK;
try {
std::map<std::string, nix::AbstractConfig::SettingInfo> settings;
nix::globalConfig.getSettings(settings);
if (settings.contains(key))
return nix_export_std_string(context, settings[key].value, value, n);
else {
return nix_set_err_msg(context, NIX_ERR_KEY, "Setting not found");
}
}
NIXC_CATCH_ERRS
}
nix_err nix_setting_set(nix_c_context *context, const char *key,
const char *value) {
if (context)
context->last_err_code = NIX_OK;
if (nix::globalConfig.set(key, value))
return NIX_OK;
else {
return nix_set_err_msg(context, NIX_ERR_KEY, "Setting not found");
}
}
nix_err nix_libutil_init(nix_c_context *context) {
if (context)
context->last_err_code = NIX_OK;
try {
nix::initLibUtil();
return NIX_OK;
}
NIXC_CATCH_ERRS
}
const char *nix_err_msg(nix_c_context *context,
const nix_c_context *read_context, unsigned int *n) {
if (context)
context->last_err_code = NIX_OK;
if (read_context->last_err) {
if (n)
*n = read_context->last_err->size();
return read_context->last_err->c_str();
}
nix_set_err_msg(context, NIX_ERR_UNKNOWN, "No error message");
return nullptr;
}
nix_err nix_err_name(nix_c_context *context, const nix_c_context *read_context,
char *value, int n) {
if (context)
context->last_err_code = NIX_OK;
if (read_context->last_err_code != NIX_ERR_NIX_ERROR) {
return nix_set_err_msg(context, NIX_ERR_UNKNOWN,
"Last error was not a nix error");
}
return nix_export_std_string(context, read_context->name, value, n);
}
nix_err nix_err_info_msg(nix_c_context *context,
const nix_c_context *read_context, char *value,
int n) {
if (context)
context->last_err_code = NIX_OK;
if (read_context->last_err_code != NIX_ERR_NIX_ERROR) {
return nix_set_err_msg(context, NIX_ERR_UNKNOWN,
"Last error was not a nix error");
}
return nix_export_std_string(context, read_context->info->msg.str(), value,
n);
}
nix_err nix_err_code(nix_c_context *context,
const nix_c_context *read_context) {
if (context)
context->last_err_code = NIX_OK;
return read_context->last_err_code;
}
// internal
nix_err nix_export_std_string(nix_c_context *context,
const std::string_view str, char *dest,
unsigned int n) {
size_t i = str.copy(dest, n - 1);
dest[i] = 0;
if (i == n - 1) {
return nix_set_err_msg(context, NIX_ERR_OVERFLOW,
"Provided buffer too short");
} else
return NIX_OK;
}

223
src/libutil/nix_api_util.h Normal file
View file

@ -0,0 +1,223 @@
#ifndef NIX_API_UTIL_H
#define NIX_API_UTIL_H
/** @file
* @brief Main entry for the libutil C bindings
*
* Also contains error handling utilities
*/
#ifdef __cplusplus
extern "C" {
#endif
// cffi start
// Error codes
/**
* @brief Type for error codes in the NIX system
*
* This type can have one of several predefined constants:
* - NIX_OK: No error occurred (0)
* - NIX_ERR_UNKNOWN: An unknown error occurred (-1)
* - NIX_ERR_OVERFLOW: An overflow error occurred (-2)
* - NIX_ERR_KEY: A key error occurred (-3)
* - NIX_ERR_NIX_ERROR: A generic Nix error occurred (-4)
*/
typedef int nix_err;
/**
* @brief No error occurred.
*
* This error code is returned when no error has occurred during the function
* execution.
*/
#define NIX_OK 0
/**
* @brief An unknown error occurred.
*
* This error code is returned when an unknown error occurred during the
* function execution.
*/
#define NIX_ERR_UNKNOWN -1
/**
* @brief An overflow error occurred.
*
* This error code is returned when an overflow error occurred during the
* function execution.
*/
#define NIX_ERR_OVERFLOW -2
/**
* @brief A key error occurred.
*
* This error code is returned when a key error occurred during the function
* execution.
*/
#define NIX_ERR_KEY -3
/**
* @brief A generic Nix error occurred.
*
* This error code is returned when a generic Nix error occurred during the
* function execution.
*/
#define NIX_ERR_NIX_ERROR -4
/**
* @brief This object stores error state.
*
* Passed as a first parameter to C functions that can fail, will store error
* information. Optional wherever it is used, passing NULL will throw a C++
* exception instead. The first field is a nix_err, that can be read directly to
* check for errors.
* @note These can be reused between different function calls,
* but make sure not to use them for multiple calls simultaneously (which can
* happen in callbacks).
*/
typedef struct nix_c_context nix_c_context;
// Function prototypes
/**
* @brief Allocate a new nix_c_context.
* @throws std::bad_alloc
* @return allocated nix_c_context, owned by the caller. Free using
* `nix_c_context_free`.
*/
nix_c_context *nix_c_context_create();
/**
* @brief Free a nix_c_context. Does not fail.
* @param[out] context The context to free, mandatory.
*/
void nix_c_context_free(nix_c_context *context);
/**
* @brief Initializes nix_libutil and its dependencies.
*
* This function can be called multiple times, but should be called at least
* once prior to any other nix function.
*
* @param[out] context Optional, stores error information
* @return NIX_OK if the initialization is successful, or an error code
* otherwise.
*/
nix_err nix_libutil_init(nix_c_context *context);
/**
* @brief Retrieves a setting from the nix global configuration.
*
* This function requires nix_libutil_init() to be called at least once prior to
* its use.
*
* @param[out] context optional, Stores error information
* @param[in] key The key of the setting to retrieve.
* @param[out] value A pointer to a buffer where the value of the setting will
* be stored.
* @param[in] n The size of the buffer pointed to by value.
* @return NIX_ERR_KEY if the setting is unknown, NIX_ERR_OVERFLOW if the
* provided buffer is too short, or NIX_OK if the setting was retrieved
* successfully.
*/
nix_err nix_setting_get(nix_c_context *context, const char *key, char *value,
int n);
/**
* @brief Sets a setting in the nix global configuration.
*
* Use "extra-<setting name>" to append to the setting's value.
*
* Settings only apply for new States. Call nix_plugins_init() when you are done
* with the settings to load any plugins.
*
* @param[out] context optional, Stores error information
* @param[in] key The key of the setting to set.
* @param[in] value The value to set for the setting.
* @return NIX_ERR_KEY if the setting is unknown, or NIX_OK if the setting was
* set successfully.
*/
nix_err nix_setting_set(nix_c_context *context, const char *key,
const char *value);
// todo: nix_plugins_init()
/**
* @brief Retrieves the nix library version.
*
* Does not fail.
* @return A static string representing the version of the nix library.
*/
const char *nix_version_get();
/**
* @brief Retrieves the most recent error message from a context.
*
* @pre This function should only be called after a previous nix function has
* returned an error.
*
* @param[out] context optional, the context to store errors in if this function
* fails
* @param[in] ctx the context to retrieve the error message from
* @param[out] n optional: a pointer to an unsigned int that is set to the
* length of the error.
* @return nullptr if no error message was ever set,
* a borrowed pointer to the error message otherwise.
*/
const char *nix_err_msg(nix_c_context *context, const nix_c_context *ctx,
unsigned int *n);
/**
* @brief Retrieves the error message from errorInfo in a context.
*
* Used to inspect nix Error messages.
*
* @pre This function should only be called after a previous nix function has
* returned a NIX_ERR_NIX_ERROR
*
* @param[out] context optional, the context to store errors in if this function
* fails
* @param[in] read_context the context to retrieve the error message from
* @param[out] value The allocated area to write the error string to.
* @param[in] n Maximum size of the returned string.
* @return NIX_OK if there were no errors, an error code otherwise.
*/
nix_err nix_err_info_msg(nix_c_context *context,
const nix_c_context *read_context, char *value, int n);
/**
* @brief Retrieves the error name from a context.
*
* Used to inspect nix Error messages.
*
* @pre This function should only be called after a previous nix function has
* returned a NIX_ERR_NIX_ERROR
*
* @param context optional, the context to store errors in if this function
* fails
* @param[in] read_context the context to retrieve the error message from
* @param[out] value The allocated area to write the error string to.
* @param[in] n Maximum size of the returned string.
* @return NIX_OK if there were no errors, an error code otherwise.
*/
nix_err nix_err_name(nix_c_context *context, const nix_c_context *read_context,
char *value, int n);
/**
* @brief Retrieves the most recent error code from a nix_c_context
*
* Equivalent to reading the first field of the context.
*
* @param[out] context optional, the context to store errors in if this function
* fails
* @param[in] read_context the context to retrieve the error message from
* @return most recent error code stored in the context.
*/
nix_err nix_err_code(nix_c_context *context, const nix_c_context *read_context);
// cffi end
#ifdef __cplusplus
}
#endif
#endif // NIX_API_UTIL_H

View file

@ -0,0 +1,61 @@
#ifndef NIX_API_UTIL_INTERNAL_H
#define NIX_API_UTIL_INTERNAL_H
#include <string>
// forward declaration
namespace nix {
class Error;
};
struct nix_c_context {
nix_err last_err_code = NIX_OK;
std::optional<std::string> last_err = {};
std::optional<nix::ErrorInfo> info = {};
std::string name = "";
};
nix_err nix_context_error(nix_c_context *context);
/**
* Internal use only.
*
* Sets the most recent error message.
*
* @param context context to write the error message to, or NULL
* @param err The error code to set and return
* @param msg The error message to set.
* @returns the error code set
*/
nix_err nix_set_err_msg(nix_c_context *context, nix_err err, const char *msg);
/**
* Internal use only.
*
* Export a std::string across the C api boundary
* @param context optional, the context to store errors in if this function
* fails
* @param str The string to export
* @param value The allocated area to write the string to.
* @param n Maximum size of the returned string.
* @return NIX_OK if there were no errors, NIX_ERR_OVERFLOW if the string length
* exceeds `n`.
*/
nix_err nix_export_std_string(nix_c_context *context,
const std::string_view str, char *dest,
unsigned int n);
#define NIXC_CATCH_ERRS \
catch (...) { \
return nix_context_error(context); \
} \
return NIX_OK;
#define NIXC_CATCH_ERRS_RES(def) \
catch (...) { \
nix_context_error(context); \
return def; \
}
#define NIXC_CATCH_ERRS_NULL NIXC_CATCH_ERRS_RES(nullptr)
#endif // NIX_API_UTIL_INTERNAL_H