/********************************************************/

/*  ntapi: Native API core library                      */

/*  Copyright (C) 2013,2014,2015  Z. Gilboa             */

/*  Released under GPLv2 and GPLv3; see COPYING.NTAPI.  */

/********************************************************/

#include <psxtypes/psxtypes.h>

#include <ntapi/ntapi.h>

#include "ntapi_impl.h"

int32_t __stdcall __ntapi_tt_get_env_var_meta_utf16(

	__in	const uint32_t *	crc32_table,

	__in	wchar16_t *		env_var_name,

	__in	uint32_t		env_var_name_hash __optional,

	__in	wchar16_t **		envp,

	__out	nt_env_var_meta_utf16 *	env_var_meta)

{

	int		idx;

	uint32_t	crc32;

	unsigned char *	byte_buffer;

	wchar16_t *	wch;

	#define EQUAL_SIGN	0x3D

	/* step 1: crc32 of the target env_var_name */

	if (env_var_name_hash)

		crc32 = env_var_name_hash;

	else {

		crc32 = 0 ^ 0xFFFFFFFF;

		/* initialize byte_buffer */

		byte_buffer = (unsigned char *)env_var_name;

		/* iterate */

		while (*byte_buffer) {

			/* two bytes at a time */

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

		}

		crc32 = (crc32 ^ 0xFFFFFFFF);

	}

	/* initialize the env_var_meta structure */

	env_var_meta->name_hash		= crc32;

	env_var_meta->name		= (wchar16_t *)0;

	env_var_meta->value		= (wchar16_t *)0;

	env_var_meta->value_hash	= 0;

	env_var_meta->envp_index	= 0;

	env_var_meta->flags		= 0;

	/* step 2: look for the environment variable in envp[] */

	idx = 0;

	while (envp[idx] && (!env_var_meta->value)) {

		wch = envp[idx];

		/* find the equal sign */

		while ((*wch) && (*wch != EQUAL_SIGN))

			wch++;

		if (*wch != EQUAL_SIGN)

			return NT_STATUS_ILLEGAL_CHARACTER;

		/* hash the current environment variable */

		crc32 = 0 ^ 0xFFFFFFFF;

		/* initialize byte_buffer */

		byte_buffer = (unsigned char *)envp[idx];

		/* iterate */

		while ((uintptr_t)(byte_buffer) < (uintptr_t)wch) {

			/* two bytes at a time */

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

		}

		if (env_var_meta->name_hash == (crc32 ^ 0xFFFFFFFF)) {

			/* found it, get ready to hash the value */

			wch++;

			env_var_meta->name	 = envp[idx];

			env_var_meta->value	 = wch;

			env_var_meta->envp_index = idx;

		} else {

			idx++;

		}

	}

	if (env_var_meta->value) {

		/* hash the value: utf-16, null-terminated */

		crc32 = 0 ^ 0xFFFFFFFF;

		/* initialize byte_buffer */

		byte_buffer = (unsigned char *)env_var_meta->value;

		/* iterate */

		while (*byte_buffer) {

			/* two bytes at a time */

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

			crc32 = (crc32 >> 8) ^ crc32_table[(crc32 ^ *byte_buffer) & 0xFF];

			byte_buffer++;

		}

		env_var_meta->value_hash = (crc32 ^ 0xFFFFFFFF);

	}

	return NT_STATUS_SUCCESS;

}