readfuncs.c

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/*-------------------------------------------------------------------------
 *
 * readfuncs.c
 *    Reader functions for Postgres tree nodes.
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/nodes/readfuncs.c
 *
 * NOTES
 *    Parse location fields are written out by outfuncs.c, but only for
 *    debugging use.  When reading a location field, we normally discard
 *    the stored value and set the location field to -1 (ie, "unknown").
 *    This is because nodes coming from a stored rule should not be thought
 *    to have a known location in the current query's text.
 *
 *    However, if restore_location_fields is true, we do restore location
 *    fields from the string.  This is currently intended only for use by the
 *    WRITE_READ_PARSE_PLAN_TREES test code, which doesn't want to cause
 *    any change in the node contents.
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <math.h>
 
#include "miscadmin.h"
#include "nodes/bitmapset.h"
#include "nodes/readfuncs.h"
 
 
/*
 * Macros to simplify reading of different kinds of fields.  Use these
 * wherever possible to reduce the chance for silly typos.  Note that these
 * hard-wire conventions about the names of the local variables in a Read
 * routine.
 */
 
/* Macros for declaring appropriate local variables */
 
/* A few guys need only local_node */
#define READ_LOCALS_NO_FIELDS(nodeTypeName) \
    nodeTypeName *local_node = makeNode(nodeTypeName)
 
/* And a few guys need only the pg_strtok support fields */
#define READ_TEMP_LOCALS()  \
    const char *token;      \
    int         length
 
/* ... but most need both */
#define READ_LOCALS(nodeTypeName)           \
    READ_LOCALS_NO_FIELDS(nodeTypeName);    \
    READ_TEMP_LOCALS()
 
/* Read an integer field (anything written as ":fldname %d") */
#define READ_INT_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = atoi(token)
 
/* Read an unsigned integer field (anything written as ":fldname %u") */
#define READ_UINT_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = atoui(token)
 
/* Read an unsigned integer field (anything written using UINT64_FORMAT) */
#define READ_UINT64_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = strtou64(token, NULL, 10)
 
/* Read a long integer field (anything written as ":fldname %ld") */
#define READ_LONG_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = atol(token)
 
/* Read an OID field (don't hard-wire assumption that OID is same as uint) */
#define READ_OID_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = atooid(token)
 
/* Read a char field (ie, one ascii character) */
#define READ_CHAR_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    /* avoid overhead of calling debackslash() for one char */ \
    local_node->fldname = (length == 0) ? '\0' : (token[0] == '\\' ? token[1] : token[0])
 
/* Read an enumerated-type field that was written as an integer code */
#define READ_ENUM_FIELD(fldname, enumtype) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = (enumtype) atoi(token)
 
/* Read a float field */
#define READ_FLOAT_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = atof(token)
 
/* Read a boolean field */
#define READ_BOOL_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = strtobool(token)
 
/* Read a character-string field */
#define READ_STRING_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = nullable_string(token, length)
 
/* Read a parse location field (and possibly throw away the value) */
#ifdef WRITE_READ_PARSE_PLAN_TREES
#define READ_LOCATION_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    local_node->fldname = restore_location_fields ? atoi(token) : -1
#else
#define READ_LOCATION_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    token = pg_strtok(&length);     /* get field value */ \
    (void) token;               /* in case not used elsewhere */ \
    local_node->fldname = -1    /* set field to "unknown" */
#endif
 
/* Read a Node field */
#define READ_NODE_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    (void) token;               /* in case not used elsewhere */ \
    local_node->fldname = nodeRead(NULL, 0)
 
/* Read a bitmapset field */
#define READ_BITMAPSET_FIELD(fldname) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    (void) token;               /* in case not used elsewhere */ \
    local_node->fldname = _readBitmapset()
 
/* Read an attribute number array */
#define READ_ATTRNUMBER_ARRAY(fldname, len) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    local_node->fldname = readAttrNumberCols(len)
 
/* Read an oid array */
#define READ_OID_ARRAY(fldname, len) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    local_node->fldname = readOidCols(len)
 
/* Read an int array */
#define READ_INT_ARRAY(fldname, len) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    local_node->fldname = readIntCols(len)
 
/* Read a bool array */
#define READ_BOOL_ARRAY(fldname, len) \
    token = pg_strtok(&length);     /* skip :fldname */ \
    local_node->fldname = readBoolCols(len)
 
/* Routine exit */
#define READ_DONE() \
    return local_node
 
 
/*
 * NOTE: use atoi() to read values written with %d, or atoui() to read
 * values written with %u in outfuncs.c.  An exception is OID values,
 * for which use atooid().  (As of 7.1, outfuncs.c writes OIDs as %u,
 * but this will probably change in the future.)
 */
#define atoui(x)  ((unsigned int) strtoul((x), NULL, 10))
 
#define strtobool(x)  ((*(x) == 't') ? true : false)
 
static char *
nullable_string(const char *token, int length)
{
    /* outToken emits <> for NULL, and pg_strtok makes that an empty string */
    if (length == 0)
        return NULL;
    /* outToken emits "" for empty string */
    if (length == 2 && token[0] == '"' && token[1] == '"')
        return pstrdup("");
    /* otherwise, we must remove protective backslashes added by outToken */
    return debackslash(token, length);
}
 
 
/*
 * _readBitmapset
 *
 * Note: this code is used in contexts where we know that a Bitmapset
 * is expected.  There is equivalent code in nodeRead() that can read a
 * Bitmapset when we come across one in other contexts.
 */
static Bitmapset *
_readBitmapset(void)
{
    Bitmapset  *result = NULL;
 
    READ_TEMP_LOCALS();
 
    token = pg_strtok(&length);
    if (token == NULL)
        elog(ERROR, "incomplete Bitmapset structure");
    if (length != 1 || token[0] != '(')
        elog(ERROR, "unrecognized token: \"%.*s\"", length, token);
 
    token = pg_strtok(&length);
    if (token == NULL)
        elog(ERROR, "incomplete Bitmapset structure");
    if (length != 1 || token[0] != 'b')
        elog(ERROR, "unrecognized token: \"%.*s\"", length, token);
 
    for (;;)
    {
        int         val;
        char       *endptr;
 
        token = pg_strtok(&length);
        if (token == NULL)
            elog(ERROR, "unterminated Bitmapset structure");
        if (length == 1 && token[0] == ')')
            break;
        val = (int) strtol(token, &endptr, 10);
        if (endptr != token + length)
            elog(ERROR, "unrecognized integer: \"%.*s\"", length, token);
        result = bms_add_member(result, val);
    }
 
    return result;
}
 
/*
 * We export this function for use by extensions that define extensible nodes.
 * That's somewhat historical, though, because calling nodeRead() will work.
 */
Bitmapset *
readBitmapset(void)
{
    return _readBitmapset();
}
 
#include "readfuncs.funcs.c"
 
 
/*
 * Support functions for nodes with custom_read_write attribute or
 * special_read_write attribute
 */
 
static Const *
_readConst(void)
{
    READ_LOCALS(Const);
 
    READ_OID_FIELD(consttype);
    READ_INT_FIELD(consttypmod);
    READ_OID_FIELD(constcollid);
    READ_INT_FIELD(constlen);
    READ_BOOL_FIELD(constbyval);
    READ_BOOL_FIELD(constisnull);
    READ_LOCATION_FIELD(location);
 
    token = pg_strtok(&length); /* skip :constvalue */
    if (local_node->constisnull)
        token = pg_strtok(&length); /* skip "<>" */
    else
        local_node->constvalue = readDatum(local_node->constbyval);
 
    READ_DONE();
}
 
static BoolExpr *
_readBoolExpr(void)
{
    READ_LOCALS(BoolExpr);
 
    /* do-it-yourself enum representation */
    token = pg_strtok(&length); /* skip :boolop */
    token = pg_strtok(&length); /* get field value */
    if (length == 3 && strncmp(token, "and", 3) == 0)
        local_node->boolop = AND_EXPR;
    else if (length == 2 && strncmp(token, "or", 2) == 0)
        local_node->boolop = OR_EXPR;
    else if (length == 3 && strncmp(token, "not", 3) == 0)
        local_node->boolop = NOT_EXPR;
    else
        elog(ERROR, "unrecognized boolop \"%.*s\"", length, token);
 
    READ_NODE_FIELD(args);
    READ_LOCATION_FIELD(location);
 
    READ_DONE();
}
 
static A_Const *
_readA_Const(void)
{
    READ_LOCALS(A_Const);
 
    /* We expect either NULL or :val here */
    token = pg_strtok(&length);
    if (length == 4 && strncmp(token, "NULL", 4) == 0)
        local_node->isnull = true;
    else
    {
        union ValUnion *tmp = nodeRead(NULL, 0);
 
        /* To forestall valgrind complaints, copy only the valid data */
        switch (nodeTag(tmp))
        {
            case T_Integer:
                memcpy(&local_node->val, tmp, sizeof(Integer));
                break;
            case T_Float:
                memcpy(&local_node->val, tmp, sizeof(Float));
                break;
            case T_Boolean:
                memcpy(&local_node->val, tmp, sizeof(Boolean));
                break;
            case T_String:
                memcpy(&local_node->val, tmp, sizeof(String));
                break;
            case T_BitString:
                memcpy(&local_node->val, tmp, sizeof(BitString));
                break;
            default:
                elog(ERROR, "unrecognized node type: %d",
                     (int) nodeTag(tmp));
                break;
        }
    }
 
    READ_LOCATION_FIELD(location);
 
    READ_DONE();
}
 
/*
 * _readConstraint
 */
static Constraint *
_readConstraint(void)
{
    READ_LOCALS(Constraint);
 
    READ_STRING_FIELD(conname);
    READ_BOOL_FIELD(deferrable);
    READ_BOOL_FIELD(initdeferred);
    READ_LOCATION_FIELD(location);
 
    token = pg_strtok(&length); /* skip :contype */
    token = pg_strtok(&length); /* get field value */
    if (length == 4 && strncmp(token, "NULL", 4) == 0)
        local_node->contype = CONSTR_NULL;
    else if (length == 8 && strncmp(token, "NOT_NULL", 8) == 0)
        local_node->contype = CONSTR_NOTNULL;
    else if (length == 7 && strncmp(token, "DEFAULT", 7) == 0)
        local_node->contype = CONSTR_DEFAULT;
    else if (length == 8 && strncmp(token, "IDENTITY", 8) == 0)
        local_node->contype = CONSTR_IDENTITY;
    else if (length == 9 && strncmp(token, "GENERATED", 9) == 0)
        local_node->contype = CONSTR_GENERATED;
    else if (length == 5 && strncmp(token, "CHECK", 5) == 0)
        local_node->contype = CONSTR_CHECK;
    else if (length == 11 && strncmp(token, "PRIMARY_KEY", 11) == 0)
        local_node->contype = CONSTR_PRIMARY;
    else if (length == 6 && strncmp(token, "UNIQUE", 6) == 0)
        local_node->contype = CONSTR_UNIQUE;
    else if (length == 9 && strncmp(token, "EXCLUSION", 9) == 0)
        local_node->contype = CONSTR_EXCLUSION;
    else if (length == 11 && strncmp(token, "FOREIGN_KEY", 11) == 0)
        local_node->contype = CONSTR_FOREIGN;
    else if (length == 15 && strncmp(token, "ATTR_DEFERRABLE", 15) == 0)
        local_node->contype = CONSTR_ATTR_DEFERRABLE;
    else if (length == 19 && strncmp(token, "ATTR_NOT_DEFERRABLE", 19) == 0)
        local_node->contype = CONSTR_ATTR_NOT_DEFERRABLE;
    else if (length == 13 && strncmp(token, "ATTR_DEFERRED", 13) == 0)
        local_node->contype = CONSTR_ATTR_DEFERRED;
    else if (length == 14 && strncmp(token, "ATTR_IMMEDIATE", 14) == 0)
        local_node->contype = CONSTR_ATTR_IMMEDIATE;
 
    switch (local_node->contype)
    {
        case CONSTR_NULL:
            /* no extra fields */
            break;
 
        case CONSTR_NOTNULL:
            READ_NODE_FIELD(keys);
            READ_INT_FIELD(inhcount);
            READ_BOOL_FIELD(is_no_inherit);
            READ_BOOL_FIELD(skip_validation);
            READ_BOOL_FIELD(initially_valid);
            break;
 
        case CONSTR_DEFAULT:
            READ_NODE_FIELD(raw_expr);
            READ_STRING_FIELD(cooked_expr);
            break;
 
        case CONSTR_IDENTITY:
            READ_NODE_FIELD(options);
            READ_CHAR_FIELD(generated_when);
            break;
 
        case CONSTR_GENERATED:
            READ_NODE_FIELD(raw_expr);
            READ_STRING_FIELD(cooked_expr);
            READ_CHAR_FIELD(generated_when);
            break;
 
        case CONSTR_CHECK:
            READ_BOOL_FIELD(is_no_inherit);
            READ_NODE_FIELD(raw_expr);
            READ_STRING_FIELD(cooked_expr);
            READ_BOOL_FIELD(skip_validation);
            READ_BOOL_FIELD(initially_valid);
            break;
 
        case CONSTR_PRIMARY:
            READ_NODE_FIELD(keys);
            READ_NODE_FIELD(including);
            READ_NODE_FIELD(options);
            READ_STRING_FIELD(indexname);
            READ_STRING_FIELD(indexspace);
            READ_BOOL_FIELD(reset_default_tblspc);
            /* access_method and where_clause not currently used */
            break;
 
        case CONSTR_UNIQUE:
            READ_BOOL_FIELD(nulls_not_distinct);
            READ_NODE_FIELD(keys);
            READ_NODE_FIELD(including);
            READ_NODE_FIELD(options);
            READ_STRING_FIELD(indexname);
            READ_STRING_FIELD(indexspace);
            READ_BOOL_FIELD(reset_default_tblspc);
            /* access_method and where_clause not currently used */
            break;
 
        case CONSTR_EXCLUSION:
            READ_NODE_FIELD(exclusions);
            READ_NODE_FIELD(including);
            READ_NODE_FIELD(options);
            READ_STRING_FIELD(indexname);
            READ_STRING_FIELD(indexspace);
            READ_BOOL_FIELD(reset_default_tblspc);
            READ_STRING_FIELD(access_method);
            READ_NODE_FIELD(where_clause);
            break;
 
        case CONSTR_FOREIGN:
            READ_NODE_FIELD(pktable);
            READ_NODE_FIELD(fk_attrs);
            READ_NODE_FIELD(pk_attrs);
            READ_CHAR_FIELD(fk_matchtype);
            READ_CHAR_FIELD(fk_upd_action);
            READ_CHAR_FIELD(fk_del_action);
            READ_NODE_FIELD(fk_del_set_cols);
            READ_NODE_FIELD(old_conpfeqop);
            READ_OID_FIELD(old_pktable_oid);
            READ_BOOL_FIELD(skip_validation);
            READ_BOOL_FIELD(initially_valid);
            break;
 
        case CONSTR_ATTR_DEFERRABLE:
        case CONSTR_ATTR_NOT_DEFERRABLE:
        case CONSTR_ATTR_DEFERRED:
        case CONSTR_ATTR_IMMEDIATE:
            /* no extra fields */
            break;
 
        default:
            elog(ERROR, "unrecognized ConstrType: %d", (int) local_node->contype);
            break;
    }
 
    READ_DONE();
}
 
static RangeTblEntry *
_readRangeTblEntry(void)
{
    READ_LOCALS(RangeTblEntry);
 
    /* put alias + eref first to make dump more legible */
    READ_NODE_FIELD(alias);
    READ_NODE_FIELD(eref);
    READ_ENUM_FIELD(rtekind, RTEKind);
 
    switch (local_node->rtekind)
    {
        case RTE_RELATION:
            READ_OID_FIELD(relid);
            READ_CHAR_FIELD(relkind);
            READ_INT_FIELD(rellockmode);
            READ_NODE_FIELD(tablesample);
            READ_UINT_FIELD(perminfoindex);
            break;
        case RTE_SUBQUERY:
            READ_NODE_FIELD(subquery);
            READ_BOOL_FIELD(security_barrier);
            /* we re-use these RELATION fields, too: */
            READ_OID_FIELD(relid);
            READ_CHAR_FIELD(relkind);
            READ_INT_FIELD(rellockmode);
            READ_UINT_FIELD(perminfoindex);
            break;
        case RTE_JOIN:
            READ_ENUM_FIELD(jointype, JoinType);
            READ_INT_FIELD(joinmergedcols);
            READ_NODE_FIELD(joinaliasvars);
            READ_NODE_FIELD(joinleftcols);
            READ_NODE_FIELD(joinrightcols);
            READ_NODE_FIELD(join_using_alias);
            break;
        case RTE_FUNCTION:
            READ_NODE_FIELD(functions);
            READ_BOOL_FIELD(funcordinality);
            break;
        case RTE_TABLEFUNC:
            READ_NODE_FIELD(tablefunc);
            /* The RTE must have a copy of the column type info, if any */
            if (local_node->tablefunc)
            {
                TableFunc  *tf = local_node->tablefunc;
 
                local_node->coltypes = tf->coltypes;
                local_node->coltypmods = tf->coltypmods;
                local_node->colcollations = tf->colcollations;
            }
            break;
        case RTE_VALUES:
            READ_NODE_FIELD(values_lists);
            READ_NODE_FIELD(coltypes);
            READ_NODE_FIELD(coltypmods);
            READ_NODE_FIELD(colcollations);
            break;
        case RTE_CTE:
            READ_STRING_FIELD(ctename);
            READ_UINT_FIELD(ctelevelsup);
            READ_BOOL_FIELD(self_reference);
            READ_NODE_FIELD(coltypes);
            READ_NODE_FIELD(coltypmods);
            READ_NODE_FIELD(colcollations);
            break;
        case RTE_NAMEDTUPLESTORE:
            READ_STRING_FIELD(enrname);
            READ_FLOAT_FIELD(enrtuples);
            READ_NODE_FIELD(coltypes);
            READ_NODE_FIELD(coltypmods);
            READ_NODE_FIELD(colcollations);
            /* we re-use these RELATION fields, too: */
            READ_OID_FIELD(relid);
            break;
        case RTE_RESULT:
            /* no extra fields */
            break;
        default:
            elog(ERROR, "unrecognized RTE kind: %d",
                 (int) local_node->rtekind);
            break;
    }
 
    READ_BOOL_FIELD(lateral);
    READ_BOOL_FIELD(inh);
    READ_BOOL_FIELD(inFromCl);
    READ_NODE_FIELD(securityQuals);
 
    READ_DONE();
}
 
static A_Expr *
_readA_Expr(void)
{
    READ_LOCALS(A_Expr);
 
    token = pg_strtok(&length);
 
    if (length == 3 && strncmp(token, "ANY", 3) == 0)
    {
        local_node->kind = AEXPR_OP_ANY;
        READ_NODE_FIELD(name);
    }
    else if (length == 3 && strncmp(token, "ALL", 3) == 0)
    {
        local_node->kind = AEXPR_OP_ALL;
        READ_NODE_FIELD(name);
    }
    else if (length == 8 && strncmp(token, "DISTINCT", 8) == 0)
    {
        local_node->kind = AEXPR_DISTINCT;
        READ_NODE_FIELD(name);
    }
    else if (length == 12 && strncmp(token, "NOT_DISTINCT", 12) == 0)
    {
        local_node->kind = AEXPR_NOT_DISTINCT;
        READ_NODE_FIELD(name);
    }
    else if (length == 6 && strncmp(token, "NULLIF", 6) == 0)
    {
        local_node->kind = AEXPR_NULLIF;
        READ_NODE_FIELD(name);
    }
    else if (length == 2 && strncmp(token, "IN", 2) == 0)
    {
        local_node->kind = AEXPR_IN;
        READ_NODE_FIELD(name);
    }
    else if (length == 4 && strncmp(token, "LIKE", 4) == 0)
    {
        local_node->kind = AEXPR_LIKE;
        READ_NODE_FIELD(name);
    }
    else if (length == 5 && strncmp(token, "ILIKE", 5) == 0)
    {
        local_node->kind = AEXPR_ILIKE;
        READ_NODE_FIELD(name);
    }
    else if (length == 7 && strncmp(token, "SIMILAR", 7) == 0)
    {
        local_node->kind = AEXPR_SIMILAR;
        READ_NODE_FIELD(name);
    }
    else if (length == 7 && strncmp(token, "BETWEEN", 7) == 0)
    {
        local_node->kind = AEXPR_BETWEEN;
        READ_NODE_FIELD(name);
    }
    else if (length == 11 && strncmp(token, "NOT_BETWEEN", 11) == 0)
    {
        local_node->kind = AEXPR_NOT_BETWEEN;
        READ_NODE_FIELD(name);
    }
    else if (length == 11 && strncmp(token, "BETWEEN_SYM", 11) == 0)
    {
        local_node->kind = AEXPR_BETWEEN_SYM;
        READ_NODE_FIELD(name);
    }
    else if (length == 15 && strncmp(token, "NOT_BETWEEN_SYM", 15) == 0)
    {
        local_node->kind = AEXPR_NOT_BETWEEN_SYM;
        READ_NODE_FIELD(name);
    }
    else if (length == 5 && strncmp(token, ":name", 5) == 0)
    {
        local_node->kind = AEXPR_OP;
        local_node->name = nodeRead(NULL, 0);
    }
    else
        elog(ERROR, "unrecognized A_Expr kind: \"%.*s\"", length, token);
 
    READ_NODE_FIELD(lexpr);
    READ_NODE_FIELD(rexpr);
    READ_LOCATION_FIELD(location);
 
    READ_DONE();
}
 
static ExtensibleNode *
_readExtensibleNode(void)
{
    const ExtensibleNodeMethods *methods;
    ExtensibleNode *local_node;
    const char *extnodename;
 
    READ_TEMP_LOCALS();
 
    token = pg_strtok(&length); /* skip :extnodename */
    token = pg_strtok(&length); /* get extnodename */
 
    extnodename = nullable_string(token, length);
    if (!extnodename)
        elog(ERROR, "extnodename has to be supplied");
    methods = GetExtensibleNodeMethods(extnodename, false);
 
    local_node = (ExtensibleNode *) newNode(methods->node_size,
                                            T_ExtensibleNode);
    local_node->extnodename = extnodename;
 
    /* deserialize the private fields */
    methods->nodeRead(local_node);
 
    READ_DONE();
}
 
 
/*
 * parseNodeString
 *
 * Given a character string representing a node tree, parseNodeString creates
 * the internal node structure.
 *
 * The string to be read must already have been loaded into pg_strtok().
 */
Node *
parseNodeString(void)
{
    READ_TEMP_LOCALS();
 
    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();
 
    token = pg_strtok(&length);
 
#define MATCH(tokname, namelen) \
    (length == namelen && memcmp(token, tokname, namelen) == 0)
 
#include "readfuncs.switch.c"
 
    elog(ERROR, "badly formatted node string \"%.32s\"...", token);
    return NULL;                /* keep compiler quiet */
}
 
 
/*
 * readDatum
 *
 * Given a string representation of a constant, recreate the appropriate
 * Datum.  The string representation embeds length info, but not byValue,
 * so we must be told that.
 */
Datum
readDatum(bool typbyval)
{
    Size        length,
                i;
    int         tokenLength;
    const char *token;
    Datum       res;
    char       *s;
 
    /*
     * read the actual length of the value
     */
    token = pg_strtok(&tokenLength);
    length = atoui(token);
 
    token = pg_strtok(&tokenLength);    /* read the '[' */
    if (token == NULL || token[0] != '[')
        elog(ERROR, "expected \"[\" to start datum, but got \"%s\"; length = %zu",
             token ? token : "[NULL]", length);
 
    if (typbyval)
    {
        if (length > (Size) sizeof(Datum))
            elog(ERROR, "byval datum but length = %zu", length);
        res = (Datum) 0;
        s = (char *) (&res);
        for (i = 0; i < (Size) sizeof(Datum); i++)
        {
            token = pg_strtok(&tokenLength);
            s[i] = (char) atoi(token);
        }
    }
    else if (length <= 0)
        res = (Datum) NULL;
    else
    {
        s = (char *) palloc(length);
        for (i = 0; i < length; i++)
        {
            token = pg_strtok(&tokenLength);
            s[i] = (char) atoi(token);
        }
        res = PointerGetDatum(s);
    }
 
    token = pg_strtok(&tokenLength);    /* read the ']' */
    if (token == NULL || token[0] != ']')
        elog(ERROR, "expected \"]\" to end datum, but got \"%s\"; length = %zu",
             token ? token : "[NULL]", length);
 
    return res;
}
 
/*
 * common implementation for scalar-array-reading functions
 *
 * The data format is either "<>" for a NULL pointer (in which case numCols
 * is ignored) or "(item item item)" where the number of items must equal
 * numCols.  The convfunc must be okay with stopping at whitespace or a
 * right parenthesis, since pg_strtok won't null-terminate the token.
 */
#define READ_SCALAR_ARRAY(fnname, datatype, convfunc) \
datatype * \
fnname(int numCols) \
{ \
    datatype   *vals; \
    READ_TEMP_LOCALS(); \
    token = pg_strtok(&length); \
    if (token == NULL) \
        elog(ERROR, "incomplete scalar array"); \
    if (length == 0) \
        return NULL;            /* it was "<>", so return NULL pointer */ \
    if (length != 1 || token[0] != '(') \
        elog(ERROR, "unrecognized token: \"%.*s\"", length, token); \
    vals = (datatype *) palloc(numCols * sizeof(datatype)); \
    for (int i = 0; i < numCols; i++) \
    { \
        token = pg_strtok(&length); \
        if (token == NULL || token[0] == ')') \
            elog(ERROR, "incomplete scalar array"); \
        vals[i] = convfunc(token); \
    } \
    token = pg_strtok(&length); \
    if (token == NULL || length != 1 || token[0] != ')') \
        elog(ERROR, "incomplete scalar array"); \
    return vals; \
}
 
/*
 * Note: these functions are exported in nodes.h for possible use by
 * extensions, so don't mess too much with their names or API.
 */
READ_SCALAR_ARRAY(readAttrNumberCols, int16, atoi)
READ_SCALAR_ARRAY(readOidCols, Oid, atooid)
/* outfuncs.c has writeIndexCols, but we don't yet need that here */
/* READ_SCALAR_ARRAY(readIndexCols, Index, atoui) */
READ_SCALAR_ARRAY(readIntCols, int, atoi)
READ_SCALAR_ARRAY(readBoolCols, bool, strtobool)