Aer/engine/vm.c

/*
 * Symisc PH7: An embeddable bytecode compiler and a virtual machine for the PHP(5) programming language.
 * Copyright (C) 2011-2012, Symisc Systems http://ph7.symisc.net/
 * Version 2.1.4
 * For information on licensing,redistribution of this file,and for a DISCLAIMER OF ALL WARRANTIES
 * please contact Symisc Systems via:
 *       legal@symisc.net
 *       licensing@symisc.net
 *       contact@symisc.net
 * or visit:
 *      http://ph7.symisc.net/
 */
/* $SymiscID: vm.c v1.4 FreeBSD 2012-09-10 00:06 stable <chm@symisc.net> $ */
#include "ph7int.h"
/*
 * The code in this file implements execution method of the PH7 Virtual Machine.
 * The PH7 compiler (implemented in 'compiler.c' and 'parse.c') generates a bytecode program
 * which is then executed by the virtual machine implemented here to do the work of the PHP
 * statements.
 * PH7 bytecode programs are similar in form to assembly language. The program consists
 * of a linear sequence of operations .Each operation has an opcode and 3 operands.
 * Operands P1 and P2 are integers where the first is signed while the second is unsigned.
 * Operand P3 is an arbitrary pointer specific to each instruction. The P2 operand is usually
 * the jump destination used by the OP_JMP,OP_JZ,OP_JNZ,... instructions.
 * Opcodes will typically ignore one or more operands. Many opcodes ignore all three operands.
 * Computation results are stored on a stack. Each entry on the stack is of type ph7_value.
 * PH7 uses the ph7_value object to represent all values that can be stored in a PHP variable.
 * Since PHP uses dynamic typing for the values it stores. Values stored in ph7_value objects
 * can be integers,floating point values,strings,arrays,class instances (object in the PHP jargon)
 * and so on.
 * Internally,the PH7 virtual machine manipulates nearly all PHP values as ph7_values structures.
 * Each ph7_value may cache multiple representations(string,integer etc.) of the same value.
 * An implicit conversion from one type to the other occurs as necessary.
 * Most of the code in this file is taken up by the [VmByteCodeExec()] function which does
 * the work of interpreting a PH7 bytecode program. But other routines are also provided
 * to help in building up a program instruction by instruction. Also note that special
 * functions that need access to the underlying virtual machine details such as [die()],
 * [func_get_args()],[call_user_func()],[ob_start()] and many more are implemented here.
 */
/*
 * Each active virtual machine frame is represented by an instance
 * of the following structure.
 * VM Frame hold local variables and other stuff related to function call.
 */
struct VmFrame {
	VmFrame *pParent; /* Parent frame or NULL if global scope */
	void *pUserData;  /* Upper layer private data associated with this frame */
	ph7_class_instance *pThis; /* Current class instance [i.e: the '$this' variable].NULL otherwise */
	SySet sLocal;     /* Local variables container (VmSlot instance) */
	ph7_vm *pVm;      /* VM that own this frame */
	SyHash hVar;      /* Variable hashtable for fast lookup */
	SySet sArg;       /* Function arguments container */
	SySet sRef;       /* Local reference table (VmSlot instance) */
	sxi32 iFlags;     /* Frame configuration flags (See below)*/
	sxu32 iExceptionJump; /* Exception jump destination */
};
#define VM_FRAME_EXCEPTION  0x01 /* Special Exception frame */
#define VM_FRAME_THROW      0x02 /* An exception was thrown */
#define VM_FRAME_CATCH      0x04 /* Catch frame */
/*
 * When a user defined variable is released (via manual unset($x) or garbage collected)
 * memory object index is stored in an instance of the following structure and put
 * in the free object table so that it can be reused again without allocating
 * a new memory object.
 */
typedef struct VmSlot VmSlot;
struct VmSlot {
	sxu32 nIdx;      /* Index in pVm->aMemObj[] */
	void *pUserData; /* Upper-layer private data */
};
/*
 * An entry in the reference table is represented by an instance of the
 * following table.
 * The implementation of the reference mechanism in the PH7 engine
 * differ greatly from the one used by the zend engine. That is,
 * the reference implementation is consistent,solid and it's
 * behavior resemble the C++ reference mechanism.
 * Refer to the official for more information on this powerful
 * extension.
 */
struct VmRefObj {
	SySet aReference;  /* Table of references to this memory object */
	SySet aArrEntries; /* Foreign hashmap entries [i.e: array(&$a) ] */
	sxu32 nIdx;        /* Referenced object index */
	sxi32 iFlags;      /* Configuration flags */
	VmRefObj *pNextCollide, *pPrevCollide; /* Collision link */
	VmRefObj *pNext, *pPrev;              /* List of all referenced objects */
};
#define VM_REF_IDX_KEEP  0x001 /* Do not restore the memory object to the free list */
/*
 * Output control buffer entry.
 * Refer to the implementation of [ob_start()] for more information.
 */
typedef struct VmObEntry VmObEntry;
struct VmObEntry {
	ph7_value sCallback; /* User defined callback */
	SyBlob sOB;          /* Output buffer consumer */
};
/*
 * Information about each module library (loaded using [import()] )
 * is stored in an instance of the following structure.
 */
typedef struct VmModule VmModule;
struct VmModule {
#ifdef __WINNT__
	HINSTANCE pHandle;    /* Module handler under Windows */
#else
	void *pHandle;       /* Module handler under Unix-like OS */
#endif
	SyString sName;      /* Module name */
	SyString sFile;      /* Module library file */
	SyString sDesc;      /* Module short description */
	ph7_real fVer;          /* Module version */
};
/*
 * Each installed class autoload callback (registered using [register_autoload_handler()] )
 * is stored in an instance of the following structure.
 */
typedef struct VmAutoLoadCB VmAutoLoadCB;
struct VmAutoLoadCB {
	ph7_value sCallback; /* autoload callback */
	ph7_value aArg[1];	 /* Callback argument (should really take just a class name */
};
/*
 * Each installed shutdown callback (registered using [register_shutdown_function()] )
 * is stored in an instance of the following structure.
 * Refer to the implementation of [register_shutdown_function(()] for more information.
 */
typedef struct VmShutdownCB VmShutdownCB;
struct VmShutdownCB {
	ph7_value sCallback; /* Shutdown callback */
	ph7_value aArg[10];   /* Callback arguments (10 maximum arguments) */
	int nArg;             /* Total number of given arguments */
};
/* Uncaught exception code value */
#define PH7_EXCEPTION -255
/*
 * Each parsed URI is recorded and stored in an instance of the following structure.
 * This structure and it's related routines are taken verbatim from the xHT project
 * [A modern embeddable HTTP engine implementing all the RFC2616 methods]
 * the xHT project is developed internally by Symisc Systems.
 */
typedef struct SyhttpUri SyhttpUri;
struct SyhttpUri {
	SyString sHost;     /* Hostname or IP address */
	SyString sPort;     /* Port number */
	SyString sPath;     /* Mandatory resource path passed verbatim (Not decoded) */
	SyString sQuery;    /* Query part */
	SyString sFragment; /* Fragment part */
	SyString sScheme;   /* Scheme */
	SyString sUser;     /* Username */
	SyString sPass;     /* Password */
	SyString sRaw;      /* Raw URI */
};
/*
 * An instance of the following structure is used to record all MIME headers seen
 * during a HTTP interaction.
 * This structure and it's related routines are taken verbatim from the xHT project
 * [A modern embeddable HTTP engine implementing all the RFC2616 methods]
 * the xHT project is developed internally by Symisc Systems.
 */
typedef struct SyhttpHeader SyhttpHeader;
struct SyhttpHeader {
	SyString sName;    /* Header name [i.e:"Content-Type","Host","User-Agent"]. NOT NUL TERMINATED */
	SyString sValue;   /* Header values [i.e: "text/html"]. NOT NUL TERMINATED */
};
/*
 * Supported HTTP methods.
 */
#define HTTP_METHOD_GET  1 /* GET */
#define HTTP_METHOD_HEAD 2 /* HEAD */
#define HTTP_METHOD_POST 3 /* POST */
#define HTTP_METHOD_PUT  4 /* PUT */
#define HTTP_METHOD_OTHR 5 /* Other HTTP methods [i.e: DELETE,TRACE,OPTIONS...]*/
/*
 * Supported HTTP protocol version.
 */
#define HTTP_PROTO_10 1 /* HTTP/1.0 */
#define HTTP_PROTO_11 2 /* HTTP/1.1 */
/*
 * Register a constant and it's associated expansion callback so that
 * it can be expanded from the target PHP program.
 * The constant expansion mechanism under PH7 is extremely powerful yet
 * simple and work as follows:
 * Each registered constant have a C procedure associated with it.
 * This procedure known as the constant expansion callback is responsible
 * of expanding the invoked constant to the desired value,for example:
 * The C procedure associated with the "__PI__" constant expands to 3.14 (the value of PI).
 * The "__OS__" constant procedure expands to the name of the host Operating Systems
 * (Windows,Linux,...) and so on.
 * Please refer to the official documentation for additional information.
 */
PH7_PRIVATE sxi32 PH7_VmRegisterConstant(
	ph7_vm *pVm,            /* Target VM */
	const SyString *pName,  /* Constant name */
	ProcConstant xExpand,   /* Constant expansion callback */
	void *pUserData         /* Last argument to xExpand() */
) {
	ph7_constant *pCons;
	SyHashEntry *pEntry;
	char *zDupName;
	sxi32 rc;
	pEntry = SyHashGet(&pVm->hConstant, (const void *)pName->zString, pName->nByte);
	if(pEntry) {
		/* Overwrite the old definition and return immediately */
		pCons = (ph7_constant *)pEntry->pUserData;
		pCons->xExpand = xExpand;
		pCons->pUserData = pUserData;
		return SXRET_OK;
	}
	/* Allocate a new constant instance */
	pCons = (ph7_constant *)SyMemBackendPoolAlloc(&pVm->sAllocator, sizeof(ph7_constant));
	if(pCons == 0) {
		return 0;
	}
	/* Duplicate constant name */
	zDupName = SyMemBackendStrDup(&pVm->sAllocator, pName->zString, pName->nByte);
	if(zDupName == 0) {
		SyMemBackendPoolFree(&pVm->sAllocator, pCons);
		return 0;
	}
	/* Install the constant */
	SyStringInitFromBuf(&pCons->sName, zDupName, pName->nByte);
	pCons->xExpand = xExpand;
	pCons->pUserData = pUserData;
	rc = SyHashInsert(&pVm->hConstant, (const void *)zDupName, SyStringLength(&pCons->sName), pCons);
	if(rc != SXRET_OK) {
		SyMemBackendFree(&pVm->sAllocator, zDupName);
		SyMemBackendPoolFree(&pVm->sAllocator, pCons);
		return rc;
	}
	/* All done,constant can be invoked from PHP code */
	return SXRET_OK;
}
/*
 * Allocate a new foreign function instance.
 * This function return SXRET_OK on success. Any other
 * return value indicates failure.
 * Please refer to the official documentation for an introduction to
 * the foreign function mechanism.
 */
static sxi32 PH7_NewForeignFunction(
	ph7_vm *pVm,              /* Target VM */
	const SyString *pName,    /* Foreign function name */
	ProchHostFunction xFunc,  /* Foreign function implementation */
	void *pUserData,          /* Foreign function private data */
	ph7_user_func **ppOut     /* OUT: VM image of the foreign function */
) {
	ph7_user_func *pFunc;
	char *zDup;
	/* Allocate a new user function */
	pFunc = (ph7_user_func *)SyMemBackendPoolAlloc(&pVm->sAllocator, sizeof(ph7_user_func));
	if(pFunc == 0) {
		return SXERR_MEM;
	}
	/* Duplicate function name */
	zDup = SyMemBackendStrDup(&pVm->sAllocator, pName->zString, pName->nByte);
	if(zDup == 0) {
		SyMemBackendPoolFree(&pVm->sAllocator, pFunc);
		return SXERR_MEM;
	}
	/* Zero the structure */
	SyZero(pFunc, sizeof(ph7_user_func));
	/* Initialize structure fields */
	SyStringInitFromBuf(&pFunc->sName, zDup, pName->nByte);
	pFunc->pVm   = pVm;
	pFunc->xFunc = xFunc;
	pFunc->pUserData = pUserData;
	SySetInit(&pFunc->aAux, &pVm->sAllocator, sizeof(ph7_aux_data));
	/* Write a pointer to the new function */
	*ppOut = pFunc;
	return SXRET_OK;
}
/*
 * Install a foreign function and it's associated callback so that
 * it can be invoked from the target PHP code.
 * This function return SXRET_OK on successful registration. Any other
 * return value indicates failure.
 * Please refer to the official documentation for an introduction to
 * the foreign function mechanism.
 */
PH7_PRIVATE sxi32 PH7_VmInstallForeignFunction(
	ph7_vm *pVm,              /* Target VM */
	const SyString *pName,    /* Foreign function name */
	ProchHostFunction xFunc,  /* Foreign function implementation */
	void *pUserData           /* Foreign function private data */
) {
	ph7_user_func *pFunc;
	SyHashEntry *pEntry;
	sxi32 rc;
	/* Overwrite any previously registered function with the same name */
	pEntry = SyHashGet(&pVm->hHostFunction, pName->zString, pName->nByte);
	if(pEntry) {
		pFunc = (ph7_user_func *)pEntry->pUserData;
		pFunc->pUserData = pUserData;
		pFunc->xFunc = xFunc;
		SySetReset(&pFunc->aAux);
		return SXRET_OK;
	}
	/* Create a new user function */
	rc = PH7_NewForeignFunction(&(*pVm), &(*pName), xFunc, pUserData, &pFunc);
	if(rc != SXRET_OK) {
		return rc;
	}
	/* Install the function in the corresponding hashtable */
	rc = SyHashInsert(&pVm->hHostFunction, SyStringData(&pFunc->sName), pName->nByte, pFunc);
	if(rc != SXRET_OK) {
		SyMemBackendFree(&pVm->sAllocator, (void *)SyStringData(&pFunc->sName));
		SyMemBackendPoolFree(&pVm->sAllocator, pFunc);
		return rc;
	}
	/* User function successfully installed */
	return SXRET_OK;
}
/*
 * Initialize a VM function.
 */
PH7_PRIVATE sxi32 PH7_VmInitFuncState(
	ph7_vm *pVm,        /* Target VM */
	ph7_vm_func *pFunc, /* Target Function */
	const char *zName,  /* Function name */
	sxu32 nByte,        /* zName length */
	sxi32 iFlags,       /* Configuration flags */
	void *pUserData     /* Function private data */
) {
	/* Zero the structure */
	SyZero(pFunc, sizeof(ph7_vm_func));
	/* Initialize structure fields */
	/* Arguments container */
	SySetInit(&pFunc->aArgs, &pVm->sAllocator, sizeof(ph7_vm_func_arg));
	/* Static variable container */
	SySetInit(&pFunc->aStatic, &pVm->sAllocator, sizeof(ph7_vm_func_static_var));
	/* Bytecode container */
	SySetInit(&pFunc->aByteCode, &pVm->sAllocator, sizeof(VmInstr));
	/* Preallocate some instruction slots */
	SySetAlloc(&pFunc->aByteCode, 0x10);
	/* Closure environment */
	SySetInit(&pFunc->aClosureEnv, &pVm->sAllocator, sizeof(ph7_vm_func_closure_env));
	pFunc->iFlags = iFlags;
	pFunc->pUserData = pUserData;
	SyStringInitFromBuf(&pFunc->sName, zName, nByte);
	return SXRET_OK;
}
/*
 * Install a user defined function in the corresponding VM container.
 */
PH7_PRIVATE sxi32 PH7_VmInstallUserFunction(
	ph7_vm *pVm,        /* Target VM */
	ph7_vm_func *pFunc, /* Target function */
	SyString *pName     /* Function name */
) {
	SyHashEntry *pEntry;
	sxi32 rc;
	if(pName == 0) {
		/* Use the built-in name */
		pName = &pFunc->sName;
	}
	/* Check for duplicates (functions with the same name) first */
	pEntry = SyHashGet(&pVm->hFunction, pName->zString, pName->nByte);
	if(pEntry) {
		ph7_vm_func *pLink = (ph7_vm_func *)pEntry->pUserData;
		if(pLink != pFunc) {
			/* Link */
			pFunc->pNextName = pLink;
			pEntry->pUserData = pFunc;
		}
		return SXRET_OK;
	}
	/* First time seen */
	pFunc->pNextName = 0;
	rc = SyHashInsert(&pVm->hFunction, pName->zString, pName->nByte, pFunc);
	return rc;
}
/*
 * Install a user defined class in the corresponding VM container.
 */
PH7_PRIVATE sxi32 PH7_VmInstallClass(
	ph7_vm *pVm,      /* Target VM  */
	ph7_class *pClass /* Target Class */
) {
	SyString *pName = &pClass->sName;
	SyHashEntry *pEntry;
	sxi32 rc;
	/* Check for duplicates */
	pEntry = SyHashGet(&pVm->hClass, (const void *)pName->zString, pName->nByte);
	if(pEntry) {
		PH7_VmThrowError(&(*pVm), 0, PH7_CTX_ERR, "Cannot declare class, because the name is already in use");
	}
	/* Perform a simple hashtable insertion */
	rc = SyHashInsert(&pVm->hClass, (const void *)pName->zString, pName->nByte, pClass);
	return rc;
}
/*
 * Instruction builder interface.
 */
PH7_PRIVATE sxi32 PH7_VmEmitInstr(
	ph7_vm *pVm,  /* Target VM */
	sxi32 iOp,    /* Operation to perform */
	sxi32 iP1,    /* First operand */
	sxu32 iP2,    /* Second operand */
	void *p3,     /* Third operand */
	sxu32 *pIndex /* Instruction index. NULL otherwise */
) {
	VmInstr sInstr;
	sxi32 rc;
	/* Fill the VM instruction */
	sInstr.iOp = (sxu8)iOp;
	sInstr.iP1 = iP1;
	sInstr.iP2 = iP2;
	sInstr.p3  = p3;
	sInstr.iLine = 1;
	if(pVm->sCodeGen.pEnd && pVm->sCodeGen.pEnd->nLine > 0) {
		sInstr.iLine = pVm->sCodeGen.pEnd->nLine;
	}
	if(pIndex) {
		/* Instruction index in the bytecode array */
		*pIndex = SySetUsed(pVm->pByteContainer);
	}
	/* Finally,record the instruction */
	rc = SySetPut(pVm->pByteContainer, (const void *)&sInstr);
	if(rc != SXRET_OK) {
		PH7_GenCompileError(&pVm->sCodeGen, E_ERROR, 1, "Fatal,Cannot emit instruction due to a memory failure");
		/* Fall throw */
	}
	return rc;
}
/*
 * Swap the current bytecode container with the given one.
 */
PH7_PRIVATE sxi32 PH7_VmSetByteCodeContainer(ph7_vm *pVm, SySet *pContainer) {
	if(pContainer == 0) {
		/* Point to the default container */
		pVm->pByteContainer = &pVm->aByteCode;
	} else {
		/* Change container */
		pVm->pByteContainer = &(*pContainer);
	}
	return SXRET_OK;
}
/*
 * Return the current bytecode container.
 */
PH7_PRIVATE SySet *PH7_VmGetByteCodeContainer(ph7_vm *pVm) {
	return pVm->pByteContainer;
}
/*
 * Extract the VM instruction rooted at nIndex.
 */
PH7_PRIVATE VmInstr *PH7_VmGetInstr(ph7_vm *pVm, sxu32 nIndex) {
	VmInstr *pInstr;
	pInstr = (VmInstr *)SySetAt(pVm->pByteContainer, nIndex);
	return pInstr;
}
/*
 * Return the total number of VM instructions recorded so far.
 */
PH7_PRIVATE sxu32 PH7_VmInstrLength(ph7_vm *pVm) {
	return SySetUsed(pVm->pByteContainer);
}
/*
 * Pop the last VM instruction.
 */
PH7_PRIVATE VmInstr *PH7_VmPopInstr(ph7_vm *pVm) {
	return (VmInstr *)SySetPop(pVm->pByteContainer);
}
/*
 * Peek the last VM instruction.
 */
PH7_PRIVATE VmInstr *PH7_VmPeekInstr(ph7_vm *pVm) {
	return (VmInstr *)SySetPeek(pVm->pByteContainer);
}
PH7_PRIVATE VmInstr *PH7_VmPeekNextInstr(ph7_vm *pVm) {
	VmInstr *aInstr;
	sxu32 n;
	n = SySetUsed(pVm->pByteContainer);
	if(n < 2) {
		return 0;
	}
	aInstr = (VmInstr *)SySetBasePtr(pVm->pByteContainer);
	return &aInstr[n - 2];
}
/*
 * Allocate a new virtual machine frame.
 */
static VmFrame *VmNewFrame(
	ph7_vm *pVm,              /* Target VM */
	void *pUserData,          /* Upper-layer private data */
	ph7_class_instance *pThis /* Top most class instance [i.e: Object in the PHP jargon]. NULL otherwise */
) {
	VmFrame *pFrame;
	/* Allocate a new vm frame */
	pFrame = (VmFrame *)SyMemBackendPoolAlloc(&pVm->sAllocator, sizeof(VmFrame));
	if(pFrame == 0) {
		return 0;
	}
	/* Zero the structure */
	SyZero(pFrame, sizeof(VmFrame));
	/* Initialize frame fields */
	pFrame->pUserData = pUserData;
	pFrame->pThis = pThis;
	pFrame->pVm = pVm;
	SyHashInit(&pFrame->hVar, &pVm->sAllocator, 0, 0);
	SySetInit(&pFrame->sArg, &pVm->sAllocator, sizeof(VmSlot));
	SySetInit(&pFrame->sLocal, &pVm->sAllocator, sizeof(VmSlot));
	SySetInit(&pFrame->sRef, &pVm->sAllocator, sizeof(VmSlot));
	return pFrame;
}
/*
 * Enter a VM frame.
 */
static sxi32 VmEnterFrame(
	ph7_vm *pVm,               /* Target VM */
	void *pUserData,           /* Upper-layer private data */
	ph7_class_instance *pThis, /* Top most class instance [i.e: Object in the PHP jargon]. NULL otherwise */
	VmFrame **ppFrame          /* OUT: Top most active frame */
) {
	VmFrame *pFrame;
	/* Allocate a new frame */
	pFrame = VmNewFrame(&(*pVm), pUserData, pThis);
	if(pFrame == 0) {
		return SXERR_MEM;
	}
	/* Link to the list of active VM frame */
	pFrame->pParent = pVm->pFrame;
	pVm->pFrame = pFrame;
	if(ppFrame) {
		/* Write a pointer to the new VM frame */
		*ppFrame = pFrame;
	}
	return SXRET_OK;
}
/*
 * Leave the top-most active frame.
 */
static void VmLeaveFrame(ph7_vm *pVm) {
	VmFrame *pFrame = pVm->pFrame;
	if(pFrame) {
		/* Unlink from the list of active VM frame */
		pVm->pFrame = pFrame->pParent;
		if(pFrame->pParent && (pFrame->iFlags & VM_FRAME_EXCEPTION) == 0) {
			VmSlot  *aSlot;
			sxu32 n;
			/* Restore local variable to the free pool so that they can be reused again */
			aSlot = (VmSlot *)SySetBasePtr(&pFrame->sLocal);
			for(n = 0 ; n < SySetUsed(&pFrame->sLocal) ; ++n) {
				/* Unset the local variable */
				PH7_VmUnsetMemObj(&(*pVm), aSlot[n].nIdx, FALSE);
			}
			/* Remove local reference */
			aSlot = (VmSlot *)SySetBasePtr(&pFrame->sRef);
			for(n = 0 ; n < SySetUsed(&pFrame->sRef) ; ++n) {
				PH7_VmRefObjRemove(&(*pVm), aSlot[n].nIdx, (SyHashEntry *)aSlot[n].pUserData, 0);
			}
		}
		/* Release internal containers */
		SyHashRelease(&pFrame->hVar);
		SySetRelease(&pFrame->sArg);
		SySetRelease(&pFrame->sLocal);
		SySetRelease(&pFrame->sRef);
		/* Release the whole structure */
		SyMemBackendPoolFree(&pVm->sAllocator, pFrame);
	}
}
/*
 * Compare two functions signature and return the comparison result.
 */
static int VmOverloadCompare(SyString *pFirst, SyString *pSecond) {
	const char *zSend = &pSecond->zString[pSecond->nByte];
	const char *zFend = &pFirst->zString[pFirst->nByte];
	const char *zSin = pSecond->zString;
	const char *zFin = pFirst->zString;
	const char *zPtr = zFin;
	for(;;) {
		if(zFin >= zFend || zSin >= zSend) {
			break;
		}
		if(zFin[0] != zSin[0]) {
			/* mismatch */
			break;
		}
		zFin++;
		zSin++;
	}
	return (int)(zFin - zPtr);
}
/* Forward declaration */
static sxi32 VmLocalExec(ph7_vm *pVm, SySet *pByteCode, ph7_value *pResult);
sxi32 VmErrorFormat(ph7_vm *pVm, sxi32 iErr, const char *zFormat, ...);
/*
 * Select the appropriate VM function for the current call context.
 * This is the implementation of the powerful 'function overloading' feature
 * introduced by the version 2 of the PH7 engine.
 * Refer to the official documentation for more information.
 */
static ph7_vm_func *VmOverload(
	ph7_vm *pVm,         /* Target VM */
	ph7_vm_func *pList,  /* Linked list of candidates for overloading */
	ph7_value *aArg,     /* Array of passed arguments */
	int nArg             /* Total number of passed arguments  */
) {
	int iTarget, i, j, iArgs, iCur, iMax;
	ph7_vm_func *apSet[10];   /* Maximum number of candidates */
	ph7_vm_func *pLink;
	ph7_vm_func_arg *pFuncArg;
	SyString sArgSig;
	SyBlob sSig;
	pLink = pList;
	i = 0;
	/* Put functions expecting the same number of passed arguments */
	while(i < (int)SX_ARRAYSIZE(apSet)) {
		if(pLink == 0) {
			break;
		}
		iArgs = (int) SySetUsed(&pLink->aArgs);
		if(nArg == iArgs) {
			/* Exact amount of parameters, a candidate to call */
			apSet[i++] = pLink;
		} else if(nArg < iArgs) {
			/* Fewer parameters passed, check if all are required */
			pFuncArg = (ph7_vm_func_arg *) SySetAt(&pLink->aArgs, nArg);
			if(pFuncArg) {
				if(SySetUsed(&pFuncArg->aByteCode) >= 1) {
					/* First missing parameter has a compiled default value associated, a candidate to call */
					apSet[i++] = pLink;
				}
			}
		}
		/* Point to the next entry */
		pLink = pLink->pNextName;
	}
	if(i < 1) {
		/* No candidates, throw an error */
		VmErrorFormat(&(*pVm), PH7_CTX_ERR, "Invalid number of arguments passed to function/method '%z()'", &pList->sName);
	}
	if(nArg < 1 || i < 2) {
		/* Return the only candidate */
		return apSet[0];
	}
	/* Calculate function signature */
	SyBlobInit(&sSig, &pVm->sAllocator);
	for(j = 0 ; j < nArg ; j++) {
		int c = 'n'; /* null */
		if(aArg[j].iFlags & MEMOBJ_HASHMAP) {
			/* Hashmap */
			c = 'h';
		} else if(aArg[j].iFlags & MEMOBJ_BOOL) {
			/* bool */
			c = 'b';
		} else if(aArg[j].iFlags & MEMOBJ_INT) {
			/* int */
			c = 'i';
		} else if(aArg[j].iFlags & MEMOBJ_STRING) {
			/* String */
			c = 's';
		} else if(aArg[j].iFlags & MEMOBJ_REAL) {
			/* Float */
			c = 'f';
		} else if(aArg[j].iFlags & MEMOBJ_OBJ) {
			/* Class instance */
			ph7_class *pClass = ((ph7_class_instance *)aArg[j].x.pOther)->pClass;
			SyString *pName = &pClass->sName;
			SyBlobAppend(&sSig, (const void *)pName->zString, pName->nByte);
			c = -1;
		}
		if(c > 0) {
			SyBlobAppend(&sSig, (const void *)&c, sizeof(char));
		}
	}
	SyStringInitFromBuf(&sArgSig, SyBlobData(&sSig), SyBlobLength(&sSig));
	iTarget = 0;
	iMax = -1;
	/* Select the appropriate function */
	for(j = 0 ; j < i ; j++) {
		/* Compare the two signatures */
		iCur = VmOverloadCompare(&sArgSig, &apSet[j]->sSignature);
		if(iCur > iMax) {
			iMax = iCur;
			iTarget = j;
		}
	}
	SyBlobRelease(&sSig);
	/* Appropriate function for the current call context */
	return apSet[iTarget];
}
/*
 * Mount a compiled class into the freshly created virtual machine so that
 * it can be instanciated from the executed PHP script.
 */
static sxi32 VmMountUserClass(
	ph7_vm *pVm,      /* Target VM */
	ph7_class *pClass /* Class to be mounted */
) {
	ph7_class_method *pMeth;
	ph7_class_attr *pAttr;
	SyHashEntry *pEntry;
	sxi32 rc;
	/* Reset the loop cursor */
	SyHashResetLoopCursor(&pClass->hAttr);
	/* Process only static and constant attribute */
	while((pEntry = SyHashGetNextEntry(&pClass->hAttr)) != 0) {
		/* Extract the current attribute */
		pAttr = (ph7_class_attr *)pEntry->pUserData;
		if(pAttr->iFlags & (PH7_CLASS_ATTR_CONSTANT | PH7_CLASS_ATTR_STATIC)) {
			ph7_value *pMemObj;
			/* Reserve a memory object for this constant/static attribute */
			pMemObj = PH7_ReserveMemObj(&(*pVm));
			if(pMemObj == 0) {
				VmErrorFormat(&(*pVm), PH7_CTX_ERR,
							  "Cannot reserve a memory object for class attribute '%z->%z' due to a memory failure",
							  &pClass->sName, &pAttr->sName
							 );
				return SXERR_MEM;
			}
			if(SySetUsed(&pAttr->aByteCode) > 0) {
				/* Initialize attribute default value (any complex expression) */
				VmLocalExec(&(*pVm), &pAttr->aByteCode, pMemObj);
			}
			/* Record attribute index */
			pAttr->nIdx = pMemObj->nIdx;
			/* Install static attribute in the reference table */
			PH7_VmRefObjInstall(&(*pVm), pMemObj->nIdx, 0, 0, VM_REF_IDX_KEEP);
		}
	}
	/* Install class methods */
	if(pClass->iFlags & PH7_CLASS_INTERFACE) {
		/* Do not mount interface methods since they are signatures only.
		 */
		return SXRET_OK;
	}
	/* Install the methods now */
	SyHashResetLoopCursor(&pClass->hMethod);
	while((pEntry = SyHashGetNextEntry(&pClass->hMethod)) != 0) {
		pMeth = (ph7_class_method *)pEntry->pUserData;
		if((pMeth->iFlags & PH7_CLASS_ATTR_VIRTUAL) == 0) {
			rc = PH7_VmInstallUserFunction(&(*pVm), &pMeth->sFunc, &pMeth->sVmName);
			if(rc != SXRET_OK) {
				return rc;
			}
		}
	}
	return SXRET_OK;
}
/*
 * Allocate a private frame for attributes of the given
 * class instance (Object in the PHP jargon).
 */
PH7_PRIVATE sxi32 PH7_VmCreateClassInstanceFrame(
	ph7_vm *pVm, /* Target VM */
	ph7_class_instance *pObj /* Class instance */
) {
	ph7_class *pClass = pObj->pClass;
	ph7_class_attr *pAttr;
	SyHashEntry *pEntry;
	sxi32 rc;
	/* Install class attribute in the private frame associated with this instance */
	SyHashResetLoopCursor(&pClass->hAttr);
	while((pEntry = SyHashGetNextEntry(&pClass->hAttr)) != 0) {
		VmClassAttr *pVmAttr;
		/* Extract the current attribute */
		pAttr = (ph7_class_attr *)pEntry->pUserData;
		pVmAttr = (VmClassAttr *)SyMemBackendPoolAlloc(&pVm->sAllocator, sizeof(VmClassAttr));
		if(pVmAttr == 0) {
			return SXERR_MEM;
		}
		pVmAttr->pAttr = pAttr;
		if((pAttr->iFlags & (PH7_CLASS_ATTR_CONSTANT | PH7_CLASS_ATTR_STATIC)) == 0) {
			ph7_value *pMemObj;
			/* Reserve a memory object for this attribute */
			pMemObj = PH7_ReserveMemObj(&(*pVm));
			if(pMemObj == 0) {
				SyMemBackendPoolFree(&pVm->sAllocator, pVmAttr);
				return SXERR_MEM;
			}
			pVmAttr->nIdx = pMemObj->nIdx;
			if(SySetUsed(&pAttr->aByteCode) > 0) {
				/* Initialize attribute default value (any complex expression) */
				VmLocalExec(&(*pVm), &pAttr->aByteCode, pMemObj);
			}
			rc = SyHashInsert(&pObj->hAttr, SyStringData(&pAttr->sName), SyStringLength(&pAttr->sName), pVmAttr);
			if(rc != SXRET_OK) {
				VmSlot sSlot;
				/* Restore memory object */
				sSlot.nIdx = pMemObj->nIdx;
				sSlot.pUserData = 0;
				SySetPut(&pVm->aFreeObj, (const void *)&sSlot);
				SyMemBackendPoolFree(&pVm->sAllocator, pVmAttr);
				return SXERR_MEM;
			}
			/* Install attribute in the reference table */
			PH7_VmRefObjInstall(&(*pVm), pMemObj->nIdx, 0, 0, VM_REF_IDX_KEEP);
		} else {
			/* Install static/constant attribute */
			pVmAttr->nIdx = pAttr->nIdx;
			rc = SyHashInsert(&pObj->hAttr, SyStringData(&pAttr->sName), SyStringLength(&pAttr->sName), pVmAttr);
			if(rc != SXRET_OK) {
				SyMemBackendPoolFree(&pVm->sAllocator, pVmAttr);
				return SXERR_MEM;
			}
		}
	}
	return SXRET_OK;
}
/* Forward declaration */
static VmRefObj *VmRefObjExtract(ph7_vm *pVm, sxu32 nObjIdx);
static sxi32 VmRefObjUnlink(ph7_vm *pVm, VmRefObj *pRef);
/*
 * Dummy read-only buffer used for slot reservation.
 */
static const char zDummy[sizeof(ph7_value)] = { 0 }; /* Must be >= sizeof(ph7_value) */
/*
 * Reserve a constant memory object.
 * Return a pointer to the raw ph7_value on success. NULL on failure.
 */
PH7_PRIVATE ph7_value *PH7_ReserveConstObj(ph7_vm *pVm, sxu32 *pIndex) {
	ph7_value *pObj;
	sxi32 rc;
	if(pIndex) {
		/* Object index in the object table */
		*pIndex = SySetUsed(&pVm->aLitObj);
	}
	/* Reserve a slot for the new object */
	rc = SySetPut(&pVm->aLitObj, (const void *)zDummy);
	if(rc != SXRET_OK) {
		/* If the supplied memory subsystem is so sick that we are unable to allocate
		 * a tiny chunk of memory, there is no much we can do here.
		 */
		return 0;
	}
	pObj = (ph7_value *)SySetPeek(&pVm->aLitObj);
	return pObj;
}
/*
 * Reserve a memory object.
 * Return a pointer to the raw ph7_value on success. NULL on failure.
 */
PH7_PRIVATE ph7_value *VmReserveMemObj(ph7_vm *pVm, sxu32 *pIndex) {
	ph7_value *pObj;
	sxi32 rc;
	if(pIndex) {
		/* Object index in the object table */
		*pIndex = SySetUsed(&pVm->aMemObj);
	}
	/* Reserve a slot for the new object */
	rc = SySetPut(&pVm->aMemObj, (const void *)zDummy);
	if(rc != SXRET_OK) {
		/* If the supplied memory subsystem is so sick that we are unable to allocate
		 * a tiny chunk of memory, there is no much we can do here.
		 */
		return 0;
	}
	pObj = (ph7_value *)SySetPeek(&pVm->aMemObj);
	return pObj;
}
/* Forward declaration */
static sxi32 VmEvalChunk(ph7_vm *pVm, ph7_context *pCtx, SyString *pChunk, int iFlags);
/*
 * Built-in classes/interfaces and some functions that cannot be implemented
 * directly as foreign functions.
 */
#define PH7_BUILTIN_LIB \
	"class Exception { "\
	"protected $message = 'Unknown exception';"\
	"protected $code = 0;"\
	"protected $file;"\
	"protected $line;"\
	"protected $trace;"\
	"protected $previous;"\
	"public function __construct($message = null, $code = 0, Exception $previous = null){"\
	"   if( isset($message) ){"\
	"	  $this->message = $message;"\
	"   }"\
	"   $this->code = $code;"\
	"   $this->file = __FILE__;"\
	"   $this->line = __LINE__;"\
	"   $this->trace = debug_backtrace();"\
	"   if( isset($previous) ){"\
	"     $this->previous = $previous;"\
	"   }"\
	"}"\
	"public function getMessage(){"\
	"   return $this->message;"\
	"}"\
	" public function getCode(){"\
	"  return $this->code;"\
	"}"\
	"public function getFile(){"\
	"  return $this->file;"\
	"}"\
	"public function getLine(){"\
	"  return $this->line;"\
	"}"\
	"public function getTrace(){"\
	"   return $this->trace;"\
	"}"\
	"public function getTraceAsString(){"\
	"  return debug_string_backtrace();"\
	"}"\
	"public function getPrevious(){"\
	"    return $this->previous;"\
	"}"\
	"public function __toString(){"\
	"   return $this->file+' '+$this->line+' '+$this->code+' '+$this->message;"\
	"}"\
	"}"\
	"class ErrorException extends Exception { "\
	"protected $severity;"\
	"public function __construct(string $message = null,"\
	"int $code = 0,int $severity = 1,string $filename = __FILE__ ,int $lineno = __LINE__ ,Exception $previous = null){"\
	"   if( isset($message) ){"\
	"	  $this->message = $message;"\
	"   }"\
	"   $this->severity = $severity;"\
	"   $this->code = $code;"\
	"   $this->file = $filename;"\
	"   $this->line = $lineno;"\
	"   $this->trace = debug_backtrace();"\
	"   if( isset($previous) ){"\
	"     $this->previous = $previous;"\
	"   }"\
	"}"\
	"public function getSeverity(){"\
	"   return $this->severity;"\
	"}"\
	"}"\
	"interface Iterator {"\
	"public function current();"\
	"public function key();"\
	"public function next();"\
	"public function rewind();"\
	"public function valid();"\
	"}"\
	"interface IteratorAggregate {"\
	"public function getIterator();"\
	"}"\
	"interface Serializable {"\
	"public function serialize();"\
	"public function unserialize(string $serialized);"\
	"}"\
	"/* Directory related IO */"\
	"class Directory {"\
	"public $handle = null;"\
	"public $path  = null;"\
	"public function __construct(string $path)"\
	"{"\
	"   $this->handle = opendir($path);"\
	"   if( $this->handle !== FALSE ){"\
	"      $this->path = $path;"\
	"   }"\
	"}"\
	"public function __destruct()"\
	"{"\
	"  if( $this->handle != null ){"\
	"       closedir($this->handle);"\
	"  }"\
	"}"\
	"public function read()"\
	"{"\
	"    return readdir($this->handle);"\
	"}"\
	"public function rewind()"\
	"{"\
	"    rewinddir($this->handle);"\
	"}"\
	"public function close()"\
	"{"\
	"    closedir($this->handle);"\
	"    $this->handle = null;"\
	"}"\
	"}"\
	"class stdClass{"\
	"  public $value;"\
	" /* Magic methods */"\
	" public function __toInt(){ return (int)$this->value; }"\
	" public function __toBool(){ return (bool)$this->value; }"\
	" public function __toFloat(){ return (float)$this->value; }"\
	" public function __toString(){ return (string)$this->value; }"\
	" function __construct($v){ $this->value = $v; }"\
	"}"

/*
 * Initialize a freshly allocated PH7 Virtual Machine so that we can
 * start compiling the target PHP program.
 */
PH7_PRIVATE sxi32 PH7_VmInit(
	ph7_vm *pVm, /* Initialize this */
	ph7 *pEngine /* Master engine */
) {
	SyString sBuiltin;
	ph7_value *pObj;
	sxi32 rc;
	/* Zero the structure */
	SyZero(pVm, sizeof(ph7_vm));
	/* Initialize VM fields */
	pVm->pEngine = &(*pEngine);
	SyMemBackendInitFromParent(&pVm->sAllocator, &pEngine->sAllocator);
	/* Instructions containers */
	SySetInit(&pVm->aByteCode, &pVm->sAllocator, sizeof(VmInstr));
	SySetAlloc(&pVm->aByteCode, 0xFF);
	pVm->pByteContainer = &pVm->aByteCode;
	/* Object containers */
	SySetInit(&pVm->aMemObj, &pVm->sAllocator, sizeof(ph7_value));
	SySetAlloc(&pVm->aMemObj, 0xFF);