edify/expr.cpp - android_bootable_recovery - Gitiles

 /*
  * Copyright (C) 2009 The Android Open Source Project
  *
  * 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.
  */

 #include "expr.h"

 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #include <string>
 #include <unordered_map>

 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>

 // Functions should:
 //
 //    - return a malloc()'d string
 //    - if Evaluate() on any argument returns NULL, return NULL.

 int BooleanString(const char* s) {
     return s[0] != '\0';
 }

 char* Evaluate(State* state, Expr* expr) {
     Value* v = expr->fn(expr->name, state, expr->argc, expr->argv);
     if (v == NULL) return NULL;
     if (v->type != VAL_STRING) {
         ErrorAbort(state, kArgsParsingFailure, "expecting string, got value type %d", v->type);
         FreeValue(v);
         return NULL;
     }
     char* result = v->data;
     free(v);
     return result;
 }

 Value* EvaluateValue(State* state, Expr* expr) {
     return expr->fn(expr->name, state, expr->argc, expr->argv);
 }

 Value* StringValue(char* str) {
     if (str == NULL) return NULL;
     Value* v = reinterpret_cast<Value*>(malloc(sizeof(Value)));
     v->type = VAL_STRING;
     v->size = strlen(str);
     v->data = str;
     return v;
 }

 void FreeValue(Value* v) {
     if (v == NULL) return;
     free(v->data);
     free(v);
 }

 Value* ConcatFn(const char* name, State* state, int argc, Expr* argv[]) {
     if (argc == 0) {
         return StringValue(strdup(""));
     }
     char** strings = reinterpret_cast<char**>(malloc(argc * sizeof(char*)));
     int i;
     for (i = 0; i < argc; ++i) {
         strings[i] = NULL;
     }
     char* result = NULL;
     int length = 0;
     for (i = 0; i < argc; ++i) {
         strings[i] = Evaluate(state, argv[i]);
         if (strings[i] == NULL) {
             goto done;
         }
         length += strlen(strings[i]);
     }

     result = reinterpret_cast<char*>(malloc(length+1));
     int p;
     p = 0;
     for (i = 0; i < argc; ++i) {
         strcpy(result+p, strings[i]);
         p += strlen(strings[i]);
     }
     result[p] = '\0';

   done:
     for (i = 0; i < argc; ++i) {
         free(strings[i]);
     }
     free(strings);
     return StringValue(result);
 }

 Value* IfElseFn(const char* name, State* state, int argc, Expr* argv[]) {
     if (argc != 2 && argc != 3) {
         state->errmsg = "ifelse expects 2 or 3 arguments";
         return NULL;
     }
     char* cond = Evaluate(state, argv[0]);
     if (cond == NULL) {
         return NULL;
     }

     if (BooleanString(cond) == true) {
         free(cond);
         return EvaluateValue(state, argv[1]);
     } else {
         if (argc == 3) {
             free(cond);
             return EvaluateValue(state, argv[2]);
         } else {
             return StringValue(cond);
         }
     }
 }

 Value* AbortFn(const char* name, State* state, int argc, Expr* argv[]) {
     char* msg = NULL;
     if (argc > 0) {
         msg = Evaluate(state, argv[0]);
     }
     if (msg) {
         state->errmsg = msg;
     } else {
         state->errmsg = "called abort()";
     }
     return NULL;
 }

 Value* AssertFn(const char* name, State* state, int argc, Expr* argv[]) {
     int i;
     for (i = 0; i < argc; ++i) {
         char* v = Evaluate(state, argv[i]);
         if (v == NULL) {
             return NULL;
         }
         int b = BooleanString(v);
         free(v);
         if (!b) {
             int len = argv[i]->end - argv[i]->start;
             state->errmsg = "assert failed: " + state->script.substr(argv[i]->start, len);
             return NULL;
         }
     }
     return StringValue(strdup(""));
 }

 Value* SleepFn(const char* name, State* state, int argc, Expr* argv[]) {
     char* val = Evaluate(state, argv[0]);
     if (val == NULL) {
         return NULL;
     }
     int v = strtol(val, NULL, 10);
     sleep(v);
     return StringValue(val);
 }

 Value* StdoutFn(const char* name, State* state, int argc, Expr* argv[]) {
     int i;
     for (i = 0; i < argc; ++i) {
         char* v = Evaluate(state, argv[i]);
         if (v == NULL) {
             return NULL;
         }
         fputs(v, stdout);
         free(v);
     }
     return StringValue(strdup(""));
 }

 Value* LogicalAndFn(const char* name, State* state,
                    int argc, Expr* argv[]) {
     char* left = Evaluate(state, argv[0]);
     if (left == NULL) return NULL;
     if (BooleanString(left) == true) {
         free(left);
         return EvaluateValue(state, argv[1]);
     } else {
         return StringValue(left);
     }
 }

 Value* LogicalOrFn(const char* name, State* state,
                    int argc, Expr* argv[]) {
     char* left = Evaluate(state, argv[0]);
     if (left == NULL) return NULL;
     if (BooleanString(left) == false) {
         free(left);
         return EvaluateValue(state, argv[1]);
     } else {
         return StringValue(left);
     }
 }

 Value* LogicalNotFn(const char* name, State* state,
                     int argc, Expr* argv[]) {
     char* val = Evaluate(state, argv[0]);
     if (val == NULL) return NULL;
     bool bv = BooleanString(val);
     free(val);
     return StringValue(strdup(bv ? "" : "t"));
 }

 Value* SubstringFn(const char* name, State* state,
                    int argc, Expr* argv[]) {
     char* needle = Evaluate(state, argv[0]);
     if (needle == NULL) return NULL;
     char* haystack = Evaluate(state, argv[1]);
     if (haystack == NULL) {
         free(needle);
         return NULL;
     }

     char* result = strdup(strstr(haystack, needle) ? "t" : "");
     free(needle);
     free(haystack);
     return StringValue(result);
 }

 Value* EqualityFn(const char* name, State* state, int argc, Expr* argv[]) {
     char* left = Evaluate(state, argv[0]);
     if (left == NULL) return NULL;
     char* right = Evaluate(state, argv[1]);
     if (right == NULL) {
         free(left);
         return NULL;
     }

     char* result = strdup(strcmp(left, right) == 0 ? "t" : "");
     free(left);
     free(right);
     return StringValue(result);
 }

 Value* InequalityFn(const char* name, State* state, int argc, Expr* argv[]) {
     char* left = Evaluate(state, argv[0]);
     if (left == NULL) return NULL;
     char* right = Evaluate(state, argv[1]);
     if (right == NULL) {
         free(left);
         return NULL;
     }

     char* result = strdup(strcmp(left, right) != 0 ? "t" : "");
     free(left);
     free(right);
     return StringValue(result);
 }

 Value* SequenceFn(const char* name, State* state, int argc, Expr* argv[]) {
     Value* left = EvaluateValue(state, argv[0]);
     if (left == NULL) return NULL;
     FreeValue(left);
     return EvaluateValue(state, argv[1]);
 }

 Value* LessThanIntFn(const char* name, State* state, int argc, Expr* argv[]) {
     if (argc != 2) {
         state->errmsg = "less_than_int expects 2 arguments";
         return NULL;
     }

     char* left;
     char* right;
     if (ReadArgs(state, argv, 2, &left, &right) < 0) return NULL;

     bool result = false;
     char* end;

     // Parse up to at least long long or 64-bit integers.
     int64_t l_int = static_cast<int64_t>(strtoll(left, &end, 10));
     if (left[0] == '\0' || *end != '\0') {
         goto done;
     }

     int64_t r_int;
     r_int = static_cast<int64_t>(strtoll(right, &end, 10));
     if (right[0] == '\0' || *end != '\0') {
         goto done;
     }

     result = l_int < r_int;

   done:
     free(left);
     free(right);
     return StringValue(strdup(result ? "t" : ""));
 }

 Value* GreaterThanIntFn(const char* name, State* state,
                         int argc, Expr* argv[]) {
     if (argc != 2) {
         state->errmsg = "greater_than_int expects 2 arguments";
         return NULL;
     }

     Expr* temp[2];
     temp[0] = argv[1];
     temp[1] = argv[0];

     return LessThanIntFn(name, state, 2, temp);
 }

 Value* Literal(const char* name, State* state, int argc, Expr* argv[]) {
     return StringValue(strdup(name));
 }

 // -----------------------------------------------------------------
 //   the function table
 // -----------------------------------------------------------------

 static std::unordered_map<std::string, Function> fn_table;

 void RegisterFunction(const std::string& name, Function fn) {
     fn_table[name] = fn;
 }

 Function FindFunction(const std::string& name) {
     if (fn_table.find(name) == fn_table.end()) {
         return nullptr;
     } else {
         return fn_table[name];
     }
 }

 void RegisterBuiltins() {
     RegisterFunction("ifelse", IfElseFn);
     RegisterFunction("abort", AbortFn);
     RegisterFunction("assert", AssertFn);
     RegisterFunction("concat", ConcatFn);
     RegisterFunction("is_substring", SubstringFn);
     RegisterFunction("stdout", StdoutFn);
     RegisterFunction("sleep", SleepFn);

     RegisterFunction("less_than_int", LessThanIntFn);
     RegisterFunction("greater_than_int", GreaterThanIntFn);
 }


 // -----------------------------------------------------------------
 //   convenience methods for functions
 // -----------------------------------------------------------------

 // Evaluate the expressions in argv, giving 'count' char* (the ... is
 // zero or more char** to put them in).  If any expression evaluates
 // to NULL, free the rest and return -1.  Return 0 on success.
 int ReadArgs(State* state, Expr* argv[], int count, ...) {
     char** args = reinterpret_cast<char**>(malloc(count * sizeof(char*)));
     va_list v;
     va_start(v, count);
     int i;
     for (i = 0; i < count; ++i) {
         args[i] = Evaluate(state, argv[i]);
         if (args[i] == NULL) {
             va_end(v);
             int j;
             for (j = 0; j < i; ++j) {
                 free(args[j]);
             }
             free(args);
             return -1;
         }
         *(va_arg(v, char**)) = args[i];
     }
     va_end(v);
     free(args);
     return 0;
 }

 // Evaluate the expressions in argv, giving 'count' Value* (the ... is
 // zero or more Value** to put them in).  If any expression evaluates
 // to NULL, free the rest and return -1.  Return 0 on success.
 int ReadValueArgs(State* state, Expr* argv[], int count, ...) {
     Value** args = reinterpret_cast<Value**>(malloc(count * sizeof(Value*)));
     va_list v;
     va_start(v, count);
     int i;
     for (i = 0; i < count; ++i) {
         args[i] = EvaluateValue(state, argv[i]);
         if (args[i] == NULL) {
             va_end(v);
             int j;
             for (j = 0; j < i; ++j) {
                 FreeValue(args[j]);
             }
             free(args);
             return -1;
         }
         *(va_arg(v, Value**)) = args[i];
     }
     va_end(v);
     free(args);
     return 0;
 }

 // Evaluate the expressions in argv, returning an array of char*
 // results.  If any evaluate to NULL, free the rest and return NULL.
 // The caller is responsible for freeing the returned array and the
 // strings it contains.
 char** ReadVarArgs(State* state, int argc, Expr* argv[]) {
     char** args = (char**)malloc(argc * sizeof(char*));
     int i = 0;
     for (i = 0; i < argc; ++i) {
         args[i] = Evaluate(state, argv[i]);
         if (args[i] == NULL) {
             int j;
             for (j = 0; j < i; ++j) {
                 free(args[j]);
             }
             free(args);
             return NULL;
         }
     }
     return args;
 }

 // Evaluate the expressions in argv, returning an array of Value*
 // results.  If any evaluate to NULL, free the rest and return NULL.
 // The caller is responsible for freeing the returned array and the
 // Values it contains.
 Value** ReadValueVarArgs(State* state, int argc, Expr* argv[]) {
     Value** args = (Value**)malloc(argc * sizeof(Value*));
     int i = 0;
     for (i = 0; i < argc; ++i) {
         args[i] = EvaluateValue(state, argv[i]);
         if (args[i] == NULL) {
             int j;
             for (j = 0; j < i; ++j) {
                 FreeValue(args[j]);
             }
             free(args);
             return NULL;
         }
     }
     return args;
 }

 // Use printf-style arguments to compose an error message to put into
 // *state.  Returns nullptr.
 Value* ErrorAbort(State* state, const char* format, ...) {
     va_list ap;
     va_start(ap, format);
     android::base::StringAppendV(&state->errmsg, format, ap);
     va_end(ap);
     return nullptr;
 }

 Value* ErrorAbort(State* state, CauseCode cause_code, const char* format, ...) {
     va_list ap;
     va_start(ap, format);
     android::base::StringAppendV(&state->errmsg, format, ap);
     va_end(ap);
     state->cause_code = cause_code;
     return nullptr;
 }

 State::State(const std::string& script, void* cookie) :
     script(script),
     cookie(cookie) {
 }
	/*
	* Copyright (C) 2009 The Android Open Source Project
	*
	* 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.
	*/

	#include "expr.h"

	#include <stdarg.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#include <string>
	#include <unordered_map>

	#include <android-base/stringprintf.h>
	#include <android-base/strings.h>

	// Functions should:
	//
	// - return a malloc()'d string
	// - if Evaluate() on any argument returns NULL, return NULL.

	int BooleanString(const char* s) {
	return s[0] != '\0';
	}

	char* Evaluate(State* state, Expr* expr) {
	Value* v = expr->fn(expr->name, state, expr->argc, expr->argv);
	if (v == NULL) return NULL;
	if (v->type != VAL_STRING) {
	ErrorAbort(state, kArgsParsingFailure, "expecting string, got value type %d", v->type);
	FreeValue(v);
	return NULL;
	}
	char* result = v->data;
	free(v);
	return result;
	}

	Value* EvaluateValue(State* state, Expr* expr) {
	return expr->fn(expr->name, state, expr->argc, expr->argv);
	}

	Value* StringValue(char* str) {
	if (str == NULL) return NULL;
	Value* v = reinterpret_cast<Value*>(malloc(sizeof(Value)));
	v->type = VAL_STRING;
	v->size = strlen(str);
	v->data = str;
	return v;
	}

	void FreeValue(Value* v) {
	if (v == NULL) return;
	free(v->data);
	free(v);
	}

	Value* ConcatFn(const char* name, State* state, int argc, Expr* argv[]) {
	if (argc == 0) {
	return StringValue(strdup(""));
	}
	char strings = reinterpret_cast<char>(malloc(argc * sizeof(char*)));
	int i;
	for (i = 0; i < argc; ++i) {
	strings[i] = NULL;
	}
	char* result = NULL;
	int length = 0;
	for (i = 0; i < argc; ++i) {
	strings[i] = Evaluate(state, argv[i]);
	if (strings[i] == NULL) {
	goto done;
	}
	length += strlen(strings[i]);
	}

	result = reinterpret_cast<char*>(malloc(length+1));
	int p;
	p = 0;
	for (i = 0; i < argc; ++i) {
	strcpy(result+p, strings[i]);
	p += strlen(strings[i]);
	}
	result[p] = '\0';

	done:
	for (i = 0; i < argc; ++i) {
	free(strings[i]);
	}
	free(strings);
	return StringValue(result);
	}

	Value* IfElseFn(const char* name, State* state, int argc, Expr* argv[]) {
	if (argc != 2 && argc != 3) {
	state->errmsg = "ifelse expects 2 or 3 arguments";
	return NULL;
	}
	char* cond = Evaluate(state, argv[0]);
	if (cond == NULL) {
	return NULL;
	}

	if (BooleanString(cond) == true) {
	free(cond);
	return EvaluateValue(state, argv[1]);
	} else {
	if (argc == 3) {
	free(cond);
	return EvaluateValue(state, argv[2]);
	} else {
	return StringValue(cond);
	}
	}
	}

	Value* AbortFn(const char* name, State* state, int argc, Expr* argv[]) {
	char* msg = NULL;
	if (argc > 0) {
	msg = Evaluate(state, argv[0]);
	}
	if (msg) {
	state->errmsg = msg;
	} else {
	state->errmsg = "called abort()";
	}
	return NULL;
	}

	Value* AssertFn(const char* name, State* state, int argc, Expr* argv[]) {
	int i;
	for (i = 0; i < argc; ++i) {
	char* v = Evaluate(state, argv[i]);
	if (v == NULL) {
	return NULL;
	}
	int b = BooleanString(v);
	free(v);
	if (!b) {
	int len = argv[i]->end - argv[i]->start;
	state->errmsg = "assert failed: " + state->script.substr(argv[i]->start, len);
	return NULL;
	}
	}
	return StringValue(strdup(""));
	}

	Value* SleepFn(const char* name, State* state, int argc, Expr* argv[]) {
	char* val = Evaluate(state, argv[0]);
	if (val == NULL) {
	return NULL;
	}
	int v = strtol(val, NULL, 10);
	sleep(v);
	return StringValue(val);
	}

	Value* StdoutFn(const char* name, State* state, int argc, Expr* argv[]) {
	int i;
	for (i = 0; i < argc; ++i) {
	char* v = Evaluate(state, argv[i]);
	if (v == NULL) {
	return NULL;
	}
	fputs(v, stdout);
	free(v);
	}
	return StringValue(strdup(""));
	}

	Value* LogicalAndFn(const char* name, State* state,
	int argc, Expr* argv[]) {
	char* left = Evaluate(state, argv[0]);
	if (left == NULL) return NULL;
	if (BooleanString(left) == true) {
	free(left);
	return EvaluateValue(state, argv[1]);
	} else {
	return StringValue(left);
	}
	}

	Value* LogicalOrFn(const char* name, State* state,
	int argc, Expr* argv[]) {
	char* left = Evaluate(state, argv[0]);
	if (left == NULL) return NULL;
	if (BooleanString(left) == false) {
	free(left);
	return EvaluateValue(state, argv[1]);
	} else {
	return StringValue(left);
	}
	}

	Value* LogicalNotFn(const char* name, State* state,
	int argc, Expr* argv[]) {
	char* val = Evaluate(state, argv[0]);
	if (val == NULL) return NULL;
	bool bv = BooleanString(val);
	free(val);
	return StringValue(strdup(bv ? "" : "t"));
	}

	Value* SubstringFn(const char* name, State* state,
	int argc, Expr* argv[]) {
	char* needle = Evaluate(state, argv[0]);
	if (needle == NULL) return NULL;
	char* haystack = Evaluate(state, argv[1]);
	if (haystack == NULL) {
	free(needle);
	return NULL;
	}

	char* result = strdup(strstr(haystack, needle) ? "t" : "");
	free(needle);
	free(haystack);
	return StringValue(result);
	}

	Value* EqualityFn(const char* name, State* state, int argc, Expr* argv[]) {
	char* left = Evaluate(state, argv[0]);
	if (left == NULL) return NULL;
	char* right = Evaluate(state, argv[1]);
	if (right == NULL) {
	free(left);
	return NULL;
	}

	char* result = strdup(strcmp(left, right) == 0 ? "t" : "");
	free(left);
	free(right);
	return StringValue(result);
	}

	Value* InequalityFn(const char* name, State* state, int argc, Expr* argv[]) {
	char* left = Evaluate(state, argv[0]);
	if (left == NULL) return NULL;
	char* right = Evaluate(state, argv[1]);
	if (right == NULL) {
	free(left);
	return NULL;
	}

	char* result = strdup(strcmp(left, right) != 0 ? "t" : "");
	free(left);
	free(right);
	return StringValue(result);
	}

	Value* SequenceFn(const char* name, State* state, int argc, Expr* argv[]) {
	Value* left = EvaluateValue(state, argv[0]);
	if (left == NULL) return NULL;
	FreeValue(left);
	return EvaluateValue(state, argv[1]);
	}

	Value* LessThanIntFn(const char* name, State* state, int argc, Expr* argv[]) {
	if (argc != 2) {
	state->errmsg = "less_than_int expects 2 arguments";
	return NULL;
	}

	char* left;
	char* right;
	if (ReadArgs(state, argv, 2, &left, &right) < 0) return NULL;

	bool result = false;
	char* end;

	// Parse up to at least long long or 64-bit integers.
	int64_t l_int = static_cast<int64_t>(strtoll(left, &end, 10));
	if (left[0] == '\0' \|\| *end != '\0') {
	goto done;
	}

	int64_t r_int;
	r_int = static_cast<int64_t>(strtoll(right, &end, 10));
	if (right[0] == '\0' \|\| *end != '\0') {
	goto done;
	}

	result = l_int < r_int;

	done:
	free(left);
	free(right);
	return StringValue(strdup(result ? "t" : ""));
	}

	Value* GreaterThanIntFn(const char* name, State* state,
	int argc, Expr* argv[]) {
	if (argc != 2) {
	state->errmsg = "greater_than_int expects 2 arguments";
	return NULL;
	}

	Expr* temp[2];
	temp[0] = argv[1];
	temp[1] = argv[0];

	return LessThanIntFn(name, state, 2, temp);
	}

	Value* Literal(const char* name, State* state, int argc, Expr* argv[]) {
	return StringValue(strdup(name));
	}

	// -----------------------------------------------------------------
	// the function table
	// -----------------------------------------------------------------

	static std::unordered_map<std::string, Function> fn_table;

	void RegisterFunction(const std::string& name, Function fn) {
	fn_table[name] = fn;
	}

	Function FindFunction(const std::string& name) {
	if (fn_table.find(name) == fn_table.end()) {
	return nullptr;
	} else {
	return fn_table[name];
	}
	}

	void RegisterBuiltins() {
	RegisterFunction("ifelse", IfElseFn);
	RegisterFunction("abort", AbortFn);
	RegisterFunction("assert", AssertFn);
	RegisterFunction("concat", ConcatFn);
	RegisterFunction("is_substring", SubstringFn);
	RegisterFunction("stdout", StdoutFn);
	RegisterFunction("sleep", SleepFn);

	RegisterFunction("less_than_int", LessThanIntFn);
	RegisterFunction("greater_than_int", GreaterThanIntFn);
	}


	// -----------------------------------------------------------------
	// convenience methods for functions
	// -----------------------------------------------------------------

	// Evaluate the expressions in argv, giving 'count' char* (the ... is
	// zero or more char** to put them in). If any expression evaluates
	// to NULL, free the rest and return -1. Return 0 on success.
	int ReadArgs(State* state, Expr* argv[], int count, ...) {
	char args = reinterpret_cast<char>(malloc(count * sizeof(char*)));
	va_list v;
	va_start(v, count);
	int i;
	for (i = 0; i < count; ++i) {
	args[i] = Evaluate(state, argv[i]);
	if (args[i] == NULL) {
	va_end(v);
	int j;
	for (j = 0; j < i; ++j) {
	free(args[j]);
	}
	free(args);
	return -1;
	}
	(va_arg(v, char*)) = args[i];
	}
	va_end(v);
	free(args);
	return 0;
	}

	// Evaluate the expressions in argv, giving 'count' Value* (the ... is
	// zero or more Value** to put them in). If any expression evaluates
	// to NULL, free the rest and return -1. Return 0 on success.
	int ReadValueArgs(State* state, Expr* argv[], int count, ...) {
	Value args = reinterpret_cast<Value>(malloc(count * sizeof(Value*)));
	va_list v;
	va_start(v, count);
	int i;
	for (i = 0; i < count; ++i) {
	args[i] = EvaluateValue(state, argv[i]);
	if (args[i] == NULL) {
	va_end(v);
	int j;
	for (j = 0; j < i; ++j) {
	FreeValue(args[j]);
	}
	free(args);
	return -1;
	}
	(va_arg(v, Value*)) = args[i];
	}
	va_end(v);
	free(args);
	return 0;
	}

	// Evaluate the expressions in argv, returning an array of char*
	// results. If any evaluate to NULL, free the rest and return NULL.
	// The caller is responsible for freeing the returned array and the
	// strings it contains.
	char** ReadVarArgs(State* state, int argc, Expr* argv[]) {
	char args = (char)malloc(argc * sizeof(char*));
	int i = 0;
	for (i = 0; i < argc; ++i) {
	args[i] = Evaluate(state, argv[i]);
	if (args[i] == NULL) {
	int j;
	for (j = 0; j < i; ++j) {
	free(args[j]);
	}
	free(args);
	return NULL;
	}
	}
	return args;
	}

	// Evaluate the expressions in argv, returning an array of Value*
	// results. If any evaluate to NULL, free the rest and return NULL.
	// The caller is responsible for freeing the returned array and the
	// Values it contains.
	Value** ReadValueVarArgs(State* state, int argc, Expr* argv[]) {
	Value args = (Value)malloc(argc * sizeof(Value*));
	int i = 0;
	for (i = 0; i < argc; ++i) {
	args[i] = EvaluateValue(state, argv[i]);
	if (args[i] == NULL) {
	int j;
	for (j = 0; j < i; ++j) {
	FreeValue(args[j]);
	}
	free(args);
	return NULL;
	}
	}
	return args;
	}

	// Use printf-style arguments to compose an error message to put into
	// *state. Returns nullptr.
	Value* ErrorAbort(State* state, const char* format, ...) {
	va_list ap;
	va_start(ap, format);
	android::base::StringAppendV(&state->errmsg, format, ap);
	va_end(ap);
	return nullptr;
	}

	Value* ErrorAbort(State* state, CauseCode cause_code, const char* format, ...) {
	va_list ap;
	va_start(ap, format);
	android::base::StringAppendV(&state->errmsg, format, ap);
	va_end(ap);
	state->cause_code = cause_code;
	return nullptr;
	}

	State::State(const std::string& script, void* cookie) :
	script(script),
	cookie(cookie) {
	}