src/common/percentrepl.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * percentrepl.c
   4  *        Common routines to replace percent placeholders in strings
   5  *
   6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/common/percentrepl.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #ifndef FRONTEND
  17 #include "postgres.h"
  18 #else
  19 #include "postgres_fe.h"
  20 #include "common/logging.h"
  21 #endif
  22
  23 #include "common/percentrepl.h"
  24 #include "lib/stringinfo.h"
  25
  26 /*
  27  * replace_percent_placeholders
  28  *
  29  * Replace percent-letter placeholders in input string with the supplied
  30  * values.  For example, to replace %f with foo and %b with bar, call
  31  *
  32  * replace_percent_placeholders(instr, "param_name", "bf", bar, foo);
  33  *
  34  * The return value is palloc'd.
  35  *
  36  * "%%" is replaced by a single "%".
  37  *
  38  * This throws an error for an unsupported placeholder or a "%" at the end of
  39  * the input string.
  40  *
  41  * A value may be NULL.  If the corresponding placeholder is found in the
  42  * input string, it will be treated as if an unsupported placeholder was used.
  43  * This allows callers to share a "letters" specification but vary the
  44  * actually supported placeholders at run time.
  45  *
  46  * This functions is meant for cases where all the values are readily
  47  * available or cheap to compute and most invocations will use most values
  48  * (for example for archive_command).  Also, it requires that all values are
  49  * strings.  It won't be a good match for things like log prefixes or prompts
  50  * that use a mix of data types and any invocation will only use a few of the
  51  * possible values.
  52  *
  53  * param_name is the name of the underlying GUC parameter, for error
  54  * reporting.  At the moment, this function is only used for GUC parameters.
  55  * If other kinds of uses were added, the error reporting would need to be
  56  * revised.
  57  */
  58 char *
  59 replace_percent_placeholders(const char *instr, const char *param_name, const char *letters,...)
  60 {
  61         StringInfoData result;
  62
  63         initStringInfo(&result);
  64
  65         for (const char *sp = instr; *sp; sp++)
  66         {
  67                 if (*sp == '%')
  68                 {
  69                         if (sp[1] == '%')
  70                         {
  71                                 /* Convert %% to a single % */
  72                                 sp++;
  73                                 appendStringInfoChar(&result, *sp);
  74                         }
  75                         else if (sp[1] == '\0')
  76                         {
  77                                 /* Incomplete escape sequence, expected a character afterward */
  78 #ifdef FRONTEND
  79                                 pg_log_error("invalid value for parameter \"%s\": \"%s\"", param_name, instr);
  80                                 pg_log_error_detail("String ends unexpectedly after escape character \"%%\".");
  81                                 exit(1);
  82 #else
  83                                 ereport(ERROR,
  84                                                 errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  85                                                 errmsg("invalid value for parameter \"%s\": \"%s\"", param_name, instr),
  86                                                 errdetail("String ends unexpectedly after escape character \"%%\"."));
  87 #endif
  88                         }
  89                         else
  90                         {
  91                                 /* Look up placeholder character */
  92                                 bool            found = false;
  93                                 va_list         ap;
  94
  95                                 sp++;
  96
  97                                 va_start(ap, letters);
  98                                 for (const char *lp = letters; *lp; lp++)
  99                                 {
 100                                         char       *val = va_arg(ap, char *);
 101
 102                                         if (*sp == *lp)
 103                                         {
 104                                                 if (val)
 105                                                 {
 106                                                         appendStringInfoString(&result, val);
 107                                                         found = true;
 108                                                 }
 109                                                 /* If val is NULL, we will report an error. */
 110                                                 break;
 111                                         }
 112                                 }
 113                                 va_end(ap);
 114                                 if (!found)
 115                                 {
 116                                         /* Unknown placeholder */
 117 #ifdef FRONTEND
 118                                         pg_log_error("invalid value for parameter \"%s\": \"%s\"", param_name, instr);
 119                                         pg_log_error_detail("String contains unexpected placeholder \"%%%c\".", *sp);
 120                                         exit(1);
 121 #else
 122                                         ereport(ERROR,
 123                                                         errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 124                                                         errmsg("invalid value for parameter \"%s\": \"%s\"", param_name, instr),
 125                                                         errdetail("String contains unexpected placeholder \"%%%c\".", *sp));
 126 #endif
 127                                 }
 128                         }
 129                 }
 130                 else
 131                 {
 132                         appendStringInfoChar(&result, *sp);
 133                 }
 134         }
 135
 136         return result.data;
 137 }