Implemented metacall link table.

source/dynlink/include/dynlink/dynlink_type.h

@@ -62,6 +62,20 @@ typedef void (*dynlink_symbol_addr)(void);					   /**< Function pointer referrin
 \
 	} while (0)
 
+#define dynlink_symbol_uncast(fn, result) \
+	do \
+	{ \
+		union \
+		{ \
+			void *ptr; \
+			dynlink_symbol_addr fn; \
+		} cast; \
+\
+		cast.fn = (fn); \
+		(result) = cast.ptr; \
+\
+	} while (0)
+
 #ifdef __cplusplus
 }
 #endif

source/metacall/include/metacall/metacall_link.h

@@ -40,7 +40,38 @@ extern "C" {
 */
 METACALL_API int metacall_link_initialize(void);
 
-// TODO: Implement dlsym hook function table
+/**
+*  @brief
+*    Register a function pointer in order to allow function
+*    interposition when loading a library, if you register a
+*    function @symbol called 'foo', when you try to dlsym (or the equivalent
+*    on every platform), you will get the pointer to @fn, even if
+*    the symbol does not exist in the library, it will work.
+*    Function interposition is required in order to hook into runtimes
+*    and dynamically interpose our functions.
+*
+*  @param[in] symbol
+*    Name of the function to be interposed
+*
+*  @param[in] fn
+*    Function pointer that will be returned by dlsym (or equivalent) when accessing to @symbol
+*
+*  @return
+*    Zero if success, different from zero otherwise
+*/
+METACALL_API int metacall_link_register(const char *symbol, void (*fn)(void));
+
+/**
+*  @brief
+*    Remove the hook previously registered
+*
+*  @param[in] symbol
+*    Name of the function to be removed
+*
+*  @return
+*    Zero if success, different from zero otherwise
+*/
+METACALL_API int metacall_link_unregister(const char *symbol);
 
 /**
 *  @brief

source/metacall/source/metacall_fork.c

@@ -1,8 +1,20 @@
 /*
  *	MetaCall Library by Parra Studios
+ *	A library for providing a foreign function interface calls.
+ *
  *	Copyright (C) 2016 - 2024 Vicente Eduardo Ferrer Garcia <[email protected]>
  *
- *	A library for providing a foreign function interface calls.
+ *	Licensed under the Apache License, Version 2.0 (the "License");
+ *	you may not use this file except in compliance with the License.
+ *	You may obtain a copy of the License at
+ *
+ *		http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *	Unless required by applicable law or agreed to in writing, software
+ *	distributed under the License is distributed on an "AS IS" BASIS,
+ *	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *	See the License for the specific language governing permissions and
+ *	limitations under the License.
  *
  */
 

source/metacall/source/metacall_link.c

@@ -1,26 +1,44 @@
-// /*
-//  *	MetaCall Library by Parra Studios
-//  *	Copyright (C) 2016 - 2024 Vicente Eduardo Ferrer Garcia <[email protected]>
-//  *
-//  *	A library for providing a foreign function interface calls.
-//  *
-//  */
-
-// /* -- Headers -- */
+/*
+ *	MetaCall Library by Parra Studios
+ *	A library for providing a foreign function interface calls.
+ *
+ *	Copyright (C) 2016 - 2024 Vicente Eduardo Ferrer Garcia <[email protected]>
+ *
+ *	Licensed under the Apache License, Version 2.0 (the "License");
+ *	you may not use this file except in compliance with the License.
+ *	You may obtain a copy of the License at
+ *
+ *		http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *	Unless required by applicable law or agreed to in writing, software
+ *	distributed under the License is distributed on an "AS IS" BASIS,
+ *	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *	See the License for the specific language governing permissions and
+ *	limitations under the License.
+ *
+ */
+
+/* -- Headers -- */
 
 #include <metacall/metacall.h>
 #include <metacall/metacall_link.h>
 
 #include <detour/detour.h>
 
+#include <dynlink/dynlink_type.h>
+
 #include <log/log.h>
 
+#include <adt/adt_set.h>
+
 #include <stdlib.h>
 
 /* -- Private Variables -- */
 
 static detour_handle detour_link_handle = NULL;
 
+static set metacall_link_table = NULL;
+
 #if defined(WIN32) || defined(_WIN32) || \
 	defined(__CYGWIN__) || defined(__CYGWIN32__) || \
 	defined(__MINGW32__) || defined(__MINGW64__)
@@ -38,7 +56,17 @@ FARPROC metacall_link_hook(HMODULE handle, LPCSTR symbol)
 
 	metacall_link_func_ptr metacall_link_trampoline = (metacall_link_func_ptr)detour_trampoline(detour_link_handle);
 
-	// TODO: Intercept if any, iterate hash map elements and invoke them
+	/* Intercept if any */
+	void *ptr = set_get(metacall_link_table, (set_key)symbol);
+
+	if (ptr != NULL)
+	{
+		dynlink_symbol_addr addr;
+
+		dynlink_symbol_cast(void *, ptr, addr);
+
+		return (FARPROC)addr;
+	}
 
 	return metacall_link_trampoline(handle, symbol);
 }
@@ -61,7 +89,15 @@ void *metacall_link_hook(void *handle, const char *symbol)
 
 	metacall_link_func_ptr metacall_link_trampoline = (metacall_link_func_ptr)detour_trampoline(detour_link_handle);
 
-	// TODO: Intercept if any, iterate hash map elements and invoke them
+	/* Intercept function if any */
+	void *ptr = set_get(metacall_link_table, (set_key)symbol);
+
+	log_write("metacall", LOG_LEVEL_DEBUG, "MetaCall detour link interception: %s -> %p", symbol, ptr);
+
+	if (ptr != NULL)
+	{
+		return ptr;
+	}
 
 	return metacall_link_trampoline(handle, symbol);
 }
@@ -90,9 +126,47 @@ int metacall_link_initialize(void)
 		}
 	}
 
+	if (metacall_link_table == NULL)
+	{
+		metacall_link_table = set_create(&hash_callback_str, &comparable_callback_str);
+
+		if (metacall_link_table == NULL)
+		{
+			log_write("metacall", LOG_LEVEL_ERROR, "MetaCall failed to create link table");
+
+			metacall_link_destroy();
+
+			return 1;
+		}
+	}
+
 	return 0;
 }
 
+int metacall_link_register(const char *symbol, void (*fn)(void))
+{
+	void *ptr;
+
+	if (metacall_link_table == NULL)
+	{
+		return 1;
+	}
+
+	dynlink_symbol_uncast(fn, ptr);
+
+	return set_insert(metacall_link_table, (set_key)symbol, ptr);
+}
+
+int metacall_link_unregister(const char *symbol)
+{
+	if (metacall_link_table == NULL)
+	{
+		return 1;
+	}
+
+	return (set_remove(metacall_link_table, (set_key)symbol) == NULL);
+}
+
 int metacall_link_destroy(void)
 {
 	int result = 0;
@@ -111,7 +185,12 @@ int metacall_link_destroy(void)
 		detour_link_handle = NULL;
 	}
 
-	// TODO: Destroy hash map
+	if (metacall_link_table != NULL)
+	{
+		set_destroy(metacall_link_table);
+
+		metacall_link_table = NULL;
+	}
 
 	return result;
 }