psqlscan_int.h

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/*-------------------------------------------------------------------------
 *
 * psqlscan_int.h
 *    lexical scanner internal declarations
 *
 * This file declares the PsqlScanStateData structure used by psqlscan.l
 * and shared by other lexers compatible with it, such as psqlscanslash.l.
 *
 * One difficult aspect of this code is that we need to work in multibyte
 * encodings that are not ASCII-safe.  A "safe" encoding is one in which each
 * byte of a multibyte character has the high bit set (it's >= 0x80).  Since
 * all our lexing rules treat all high-bit-set characters alike, we don't
 * really need to care whether such a byte is part of a sequence or not.
 * In an "unsafe" encoding, we still expect the first byte of a multibyte
 * sequence to be >= 0x80, but later bytes might not be.  If we scan such
 * a sequence as-is, the lexing rules could easily be fooled into matching
 * such bytes to ordinary ASCII characters.  Our solution for this is to
 * substitute 0xFF for each non-first byte within the data presented to flex.
 * The flex rules will then pass the FF's through unmolested.  The
 * psqlscan_emit() subroutine is responsible for looking back to the original
 * string and replacing FF's with the corresponding original bytes.
 *
 * Another interesting thing we do here is scan different parts of the same
 * input with physically separate flex lexers (ie, lexers written in separate
 * .l files).  We can get away with this because the only part of the
 * persistent state of a flex lexer that depends on its parsing rule tables
 * is the start state number, which is easy enough to manage --- usually,
 * in fact, we just need to set it to INITIAL when changing lexers.  But to
 * make that work at all, we must use re-entrant lexers, so that all the
 * relevant state is in the yyscan_t attached to the PsqlScanState;
 * if we were using lexers with separate static state we would soon end up
 * with dangling buffer pointers in one or the other.  Also note that this
 * is unlikely to work very nicely if the lexers aren't all built with the
 * same flex version, or if they don't use the same flex options.
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/fe_utils/psqlscan_int.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PSQLSCAN_INT_H
#define PSQLSCAN_INT_H
 
#include "fe_utils/psqlscan.h"
 
/*
 * These are just to allow this file to be compilable standalone for header
 * validity checking; in actual use, this file should always be included
 * from the body of a flex file, where these symbols are already defined.
 */
#ifndef YY_TYPEDEF_YY_BUFFER_STATE
#define YY_TYPEDEF_YY_BUFFER_STATE
typedef struct yy_buffer_state *YY_BUFFER_STATE;
#endif
#ifndef YY_TYPEDEF_YY_SCANNER_T
#define YY_TYPEDEF_YY_SCANNER_T
typedef void *yyscan_t;
#endif
 
/*
 * We use a stack of flex buffers to handle substitution of psql variables.
 * Each stacked buffer contains the as-yet-unread text from one psql variable.
 * When we pop the stack all the way, we resume reading from the outer buffer
 * identified by scanbufhandle.
 */
typedef struct StackElem
{
    YY_BUFFER_STATE buf;        /* flex input control structure */
    char       *bufstring;      /* data actually being scanned by flex */
    char       *origstring;     /* copy of original data, if needed */
    char       *varname;        /* name of variable providing data, or NULL */
    struct StackElem *next;
} StackElem;
 
/*
 * All working state of the lexer must be stored in PsqlScanStateData
 * between calls.  This allows us to have multiple open lexer operations,
 * which is needed for nested include files.  The lexer itself is not
 * recursive, but it must be re-entrant.
 */
typedef struct PsqlScanStateData
{
    yyscan_t    scanner;        /* Flex's state for this PsqlScanState */
 
    PQExpBuffer output_buf;     /* current output buffer */
 
    StackElem  *buffer_stack;   /* stack of variable expansion buffers */
 
    /*
     * These variables always refer to the outer buffer, never to any stacked
     * variable-expansion buffer.
     */
    YY_BUFFER_STATE scanbufhandle;
    char       *scanbuf;        /* start of outer-level input buffer */
    const char *scanline;       /* current input line at outer level */
 
    /* safe_encoding, curline, refline are used by emit() to replace FFs */
    int         encoding;       /* encoding being used now */
    bool        safe_encoding;  /* is current encoding "safe"? */
    bool        std_strings;    /* are string literals standard? */
    const char *curline;        /* actual flex input string for cur buf */
    const char *refline;        /* original data for cur buffer */
 
    /*
     * All this state lives across successive input lines, until explicitly
     * reset by psql_scan_reset.  start_state is adopted by yylex() on entry,
     * and updated with its finishing state on exit.
     */
    int         start_state;    /* yylex's starting/finishing state */
    int         state_before_str_stop;  /* start cond. before end quote */
    int         paren_depth;    /* depth of nesting in parentheses */
    int         xcdepth;        /* depth of nesting in slash-star comments */
    char       *dolqstart;      /* current $foo$ quote start string */
 
    /*
     * State to track boundaries of BEGIN ... END blocks in function
     * definitions, so that semicolons do not send query too early.
     */
    int         identifier_count;   /* identifiers since start of statement */
    char        identifiers[4]; /* records the first few identifiers */
    int         begin_depth;    /* depth of begin/end pairs */
 
    /*
     * Callback functions provided by the program making use of the lexer,
     * plus a void* callback passthrough argument.
     */
    const PsqlScanCallbacks *callbacks;
    void       *cb_passthrough;
} PsqlScanStateData;
 
 
/*
 * Functions exported by psqlscan.l, but only meant for use within
 * compatible lexers.
 */
extern void psqlscan_push_new_buffer(PsqlScanState state,
                                     const char *newstr, const char *varname);
extern void psqlscan_pop_buffer_stack(PsqlScanState state);
extern void psqlscan_select_top_buffer(PsqlScanState state);
extern bool psqlscan_var_is_current_source(PsqlScanState state,
                                           const char *varname);
extern YY_BUFFER_STATE psqlscan_prepare_buffer(PsqlScanState state,
                                               const char *txt, int len,
                                               char **txtcopy);
extern void psqlscan_emit(PsqlScanState state, const char *txt, int len);
extern char *psqlscan_extract_substring(PsqlScanState state,
                                        const char *txt, int len);
extern void psqlscan_escape_variable(PsqlScanState state,
                                     const char *txt, int len,
                                     PsqlScanQuoteType quote);
extern void psqlscan_test_variable(PsqlScanState state,
                                   const char *txt, int len);
 
#endif                          /* PSQLSCAN_INT_H */