/*-------------------------------------------------------------------------

 *

 * read.c

 *    routines to convert a string (legal ascii representation of node) back

 *    to nodes

 *

 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 *

 *

 * IDENTIFICATION

 *    src/backend/nodes/read.c

 *

 * HISTORY

 *    AUTHOR      DATE      MAJOR EVENT

 *    Andrew Yu     Nov 2, 1994   file creation

 *

 *-------------------------------------------------------------------------

 */

#include "postgres.h"

#include <ctype.h>

#include "common/string.h"

#include "nodes/bitmapset.h"

#include "nodes/pg_list.h"

#include "nodes/readfuncs.h"

#include "nodes/value.h"

/* Static state for pg_strtok */

static const char *pg_strtok_ptr = NULL;

/* State flag that determines how readfuncs.c should treat location fields */

#ifdef DEBUG_NODE_TESTS_ENABLED

bool    restore_location_fields = false;

#endif

/*

 * stringToNode -

 *    builds a Node tree from its string representation (assumed valid)

 *

 * restore_loc_fields instructs readfuncs.c whether to restore location

 * fields rather than set them to -1.  This is currently only supported

 * in builds with DEBUG_NODE_TESTS_ENABLED defined.

 */

static void *

stringToNodeInternal(const char *str, bool restore_loc_fields)

{

  void     *retval;

  const char *save_strtok;

#ifdef DEBUG_NODE_TESTS_ENABLED

  bool    save_restore_location_fields;

#endif

  /*

   * We save and restore the pre-existing state of pg_strtok. This makes the

   * world safe for re-entrant invocation of stringToNode, without incurring

   * a lot of notational overhead by having to pass the next-character

   * pointer around through all the readfuncs.c code.

   */

  save_strtok = pg_strtok_ptr;

  pg_strtok_ptr = str;    /* point pg_strtok at the string to read */

  /*

   * If enabled, likewise save/restore the location field handling flag.

   */

#ifdef DEBUG_NODE_TESTS_ENABLED

  save_restore_location_fields = restore_location_fields;

  restore_location_fields = restore_loc_fields;

#endif

  retval = nodeRead(NULL, 0); /* do the reading */

  pg_strtok_ptr = save_strtok;

#ifdef DEBUG_NODE_TESTS_ENABLED

  restore_location_fields = save_restore_location_fields;

#endif

  return retval;

}

/*

 * Externally visible entry points

 */

void *

stringToNode(const char *str)

{

  return stringToNodeInternal(str, false);

}

#ifdef DEBUG_NODE_TESTS_ENABLED

void *

stringToNodeWithLocations(const char *str)

{

  return stringToNodeInternal(str, true);

}

#endif

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

 *

 * the lisp token parser

 *

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

/*

 * pg_strtok --- retrieve next "token" from a string.

 *

 * Works kinda like strtok, except it never modifies the source string.

 * (Instead of storing nulls into the string, the length of the token

 * is returned to the caller.)

 * Also, the rules about what is a token are hard-wired rather than being

 * configured by passing a set of terminating characters.

 *

 * The string is assumed to have been initialized already by stringToNode.

 *

 * The rules for tokens are:

 *  * Whitespace (space, tab, newline) always separates tokens.

 *  * The characters '(', ')', '{', '}' form individual tokens even

 *    without any whitespace around them.

 *  * Otherwise, a token is all the characters up to the next whitespace

 *    or occurrence of one of the four special characters.

 *  * A backslash '\' can be used to quote whitespace or one of the four

 *    special characters, so that it is treated as a plain token character.

 *    Backslashes themselves must also be backslashed for consistency.

 *    Any other character can be, but need not be, backslashed as well.

 *  * If the resulting token is '<>' (with no backslash), it is returned

 *    as a non-NULL pointer to the token but with length == 0.  Note that

 *    there is no other way to get a zero-length token.

 *

 * Returns a pointer to the start of the next token, and the length of the

 * token (including any embedded backslashes!) in *length.  If there are

 * no more tokens, NULL and 0 are returned.

 *

 * NOTE: this routine doesn't remove backslashes; the caller must do so

 * if necessary (see "debackslash").

 *

 * NOTE: prior to release 7.0, this routine also had a special case to treat

 * a token starting with '"' as extending to the next '"'.  This code was

 * broken, however, since it would fail to cope with a string containing an

 * embedded '"'.  I have therefore removed this special case, and instead

 * introduced rules for using backslashes to quote characters.  Higher-level

 * code should add backslashes to a string constant to ensure it is treated

 * as a single token.

 */

const char *

pg_strtok(int *length)

{

  const char *local_str;    /* working pointer to string */

  const char *ret_str;    /* start of token to return */

  local_str = pg_strtok_ptr;

  while (*local_str == ' ' || *local_str == '\n' || *local_str == '\t')

    local_str++;

  if (*local_str == '\0')

  {

    *length = 0;

    pg_strtok_ptr = local_str;

    return NULL;      /* no more tokens */

  }

  /*

   * Now pointing at start of next token.

   */

  ret_str = local_str;

  if (*local_str == '(' || *local_str == ')' ||

    *local_str == '{' || *local_str == '}')

  {

    /* special 1-character token */

    local_str++;

  }

  else

  {

    /* Normal token, possibly containing backslashes */

    while (*local_str != '\0' &&

         *local_str != ' ' && *local_str != '\n' &&

         *local_str != '\t' &&

         *local_str != '(' && *local_str != ')' &&

         *local_str != '{' && *local_str != '}')

    {

      if (*local_str == '\\' && local_str[1] != '\0')

        local_str += 2;

      else

        local_str++;

    }

  }

  *length = local_str - ret_str;

  /* Recognize special case for "empty" token */

  if (*length == 2 && ret_str[0] == '<' && ret_str[1] == '>')

    *length = 0;

  pg_strtok_ptr = local_str;

  return ret_str;

}

/*

 * debackslash -

 *    create a palloc'd string holding the given token.

 *    any protective backslashes in the token are removed.

 */

char *

debackslash(const char *token, int length)

{

  char     *result = palloc(length + 1);

  char     *ptr = result;

  while (length > 0)

  {

    if (*token == '\\' && length > 1)

      token++, length--;

    *ptr++ = *token++;

    length--;

  }

  *ptr = '\0';

  return result;

}

#define RIGHT_PAREN (1000000 + 1)

#define LEFT_PAREN  (1000000 + 2)

#define LEFT_BRACE  (1000000 + 3)

#define OTHER_TOKEN (1000000 + 4)

/*

 * nodeTokenType -

 *    returns the type of the node token contained in token.

 *    It returns one of the following valid NodeTags:

 *    T_Integer, T_Float, T_Boolean, T_String, T_BitString

 *    and some of its own:

 *    RIGHT_PAREN, LEFT_PAREN, LEFT_BRACE, OTHER_TOKEN

 *

 *    Assumption: the ascii representation is legal

 */

static NodeTag

nodeTokenType(const char *token, int length)

{

  NodeTag   retval;

  const char *numptr;

  int     numlen;

  /*

   * Check if the token is a number

   */

  numptr = token;

  numlen = length;

  if (*numptr == '+' || *numptr == '-')

    numptr++, numlen--;

  if ((numlen > 0 && isdigit((unsigned char) *numptr)) ||

    (numlen > 1 && *numptr == '.' && isdigit((unsigned char) numptr[1])))

  {

    /*

     * Yes.  Figure out whether it is integral or float; this requires

     * both a syntax check and a range check. strtoint() can do both for

     * us. We know the token will end at a character that strtoint will

     * stop at, so we do not need to modify the string.

     */

    char     *endptr;

    errno = 0;

    (void) strtoint(numptr, &endptr, 10);

    if (endptr != token + length || errno == ERANGE)

      return T_Float;

    return T_Integer;

  }

  /*

   * these three cases do not need length checks, since pg_strtok() will

   * always treat them as single-byte tokens

   */

  else if (*token == '(')

    retval = LEFT_PAREN;

  else if (*token == ')')

    retval = RIGHT_PAREN;

  else if (*token == '{')

    retval = LEFT_BRACE;

  else if ((length == 4 && strncmp(token, "true", 4) == 0) ||

       (length == 5 && strncmp(token, "false", 5) == 0))

    retval = T_Boolean;

  else if (*token == '"' && length > 1 && token[length - 1] == '"')

    retval = T_String;

  else if (*token == 'b' || *token == 'x')

    retval = T_BitString;

  else

    retval = OTHER_TOKEN;

  return retval;

}

/*

 * nodeRead -

 *    Slightly higher-level reader.

 *

 * This routine applies some semantic knowledge on top of the purely

 * lexical tokenizer pg_strtok().   It can read

 *  * Value token nodes (integers, floats, booleans, or strings);

 *  * General nodes (via parseNodeString() from readfuncs.c);

 *  * Lists of the above;

 *  * Lists of integers, OIDs, or TransactionIds.

 * The return value is declared void *, not Node *, to avoid having to

 * cast it explicitly in callers that assign to fields of different types.

 *

 * External callers should always pass NULL/0 for the arguments.  Internally

 * a non-NULL token may be passed when the upper recursion level has already

 * scanned the first token of a node's representation.

 *

 * We assume pg_strtok is already initialized with a string to read (hence

 * this should only be invoked from within a stringToNode operation).

 */

void *

nodeRead(const char *token, int tok_len)

{

  Node     *result;

  NodeTag   type;

  if (token == NULL)     /* need to read a token? */

  {

    token = pg_strtok(&tok_len);

    if (token == NULL)   /* end of input */

      return NULL;

  }

  type = nodeTokenType(token, tok_len);

  switch ((int) type)

  {

    case LEFT_BRACE:

      result = parseNodeString();

      token = pg_strtok(&tok_len);

      if (token == NULL || token[0] != '}')

        elog(ERROR, "did not find '}' at end of input node");

      break;

    case LEFT_PAREN:

      {

        List     *l = NIL;

        /*----------

         * Could be an integer list:  (i int int ...)

         * or an OID list:        (o int int ...)

         * or an XID list:        (x int int ...)

         * or a bitmapset:        (b int int ...)

         * or a list of nodes/values: (node node ...)

         *----------

         */

        token = pg_strtok(&tok_len);

        if (token == NULL)

          elog(ERROR, "unterminated List structure");

        if (tok_len == 1 && token[0] == 'i')

        {

          /* List of integers */

          for (;;)

          {

            int     val;

            char     *endptr;

            token = pg_strtok(&tok_len);

            if (token == NULL)

              elog(ERROR, "unterminated List structure");

            if (token[0] == ')')

              break;

            val = (int) strtol(token, &endptr, 10);

            if (endptr != token + tok_len)

              elog(ERROR, "unrecognized integer: \"%.*s\"",

                 tok_len, token);

            l = lappend_int(l, val);

          }

          result = (Node *) l;

        }

        else if (tok_len == 1 && token[0] == 'o')

        {

          /* List of OIDs */

          for (;;)

          {

            Oid     val;

            char     *endptr;

            token = pg_strtok(&tok_len);

            if (token == NULL)

              elog(ERROR, "unterminated List structure");

            if (token[0] == ')')

              break;

            val = (Oid) strtoul(token, &endptr, 10);

            if (endptr != token + tok_len)

              elog(ERROR, "unrecognized OID: \"%.*s\"",

                 tok_len, token);

            l = lappend_oid(l, val);

          }

          result = (Node *) l;

        }

        else if (tok_len == 1 && token[0] == 'x')

        {

          /* List of TransactionIds */

          for (;;)

          {

            TransactionId val;

            char     *endptr;

            token = pg_strtok(&tok_len);

            if (token == NULL)

              elog(ERROR, "unterminated List structure");

            if (token[0] == ')')

              break;

            val = (TransactionId) strtoul(token, &endptr, 10);

            if (endptr != token + tok_len)

              elog(ERROR, "unrecognized Xid: \"%.*s\"",

                 tok_len, token);

            l = lappend_xid(l, val);

          }

          result = (Node *) l;

        }

        else if (tok_len == 1 && token[0] == 'b')

        {

          /* Bitmapset -- see also _readBitmapset() */

          Bitmapset  *bms = NULL;

          for (;;)

          {

            int     val;

            char     *endptr;

            token = pg_strtok(&tok_len);

            if (token == NULL)

              elog(ERROR, "unterminated Bitmapset structure");

            if (tok_len == 1 && token[0] == ')')

              break;

            val = (int) strtol(token, &endptr, 10);

            if (endptr != token + tok_len)

              elog(ERROR, "unrecognized integer: \"%.*s\"",

                 tok_len, token);

            bms = bms_add_member(bms, val);

          }

          result = (Node *) bms;

        }

        else

        {

          /* List of other node types */

          for (;;)

          {

            /* We have already scanned next token... */

            if (token[0] == ')')

              break;

            l = lappend(l, nodeRead(token, tok_len));

            token = pg_strtok(&tok_len);

            if (token == NULL)

              elog(ERROR, "unterminated List structure");

          }

          result = (Node *) l;

        }

        break;

      }

    case RIGHT_PAREN:

      elog(ERROR, "unexpected right parenthesis");

      result = NULL;    /* keep compiler happy */

      break;

    case OTHER_TOKEN:

      if (tok_len == 0)

      {

        /* must be "<>" --- represents a null pointer */

        result = NULL;

      }

      else

      {

        elog(ERROR, "unrecognized token: \"%.*s\"", tok_len, token);

        result = NULL;  /* keep compiler happy */

      }

      break;

    case T_Integer:

      /*

       * we know that the token terminates on a char atoi will stop at

       */

      result = (Node *) makeInteger(atoi(token));

      break;

    case T_Float:

      {

        char     *fval = (char *) palloc(tok_len + 1);

        memcpy(fval, token, tok_len);

        fval[tok_len] = '\0';

        result = (Node *) makeFloat(fval);

      }

      break;

    case T_Boolean:

      result = (Node *) makeBoolean(token[0] == 't');

      break;

    case T_String:

      /* need to remove leading and trailing quotes, and backslashes */

      result = (Node *) makeString(debackslash(token + 1, tok_len - 2));

      break;

    case T_BitString:

      /* need to remove backslashes, but there are no quotes */

      result = (Node *) makeBitString(debackslash(token, tok_len));

      break;

    default:

      elog(ERROR, "unrecognized node type: %d", (int) type);

      result = NULL;    /* keep compiler happy */

      break;

  }

  return result;

}