PostgreSQL Source Code  git master
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros
read.c
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * read.c
4  * routines to convert a string (legal ascii representation of node) back
5  * to nodes
6  *
7  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  *
11  * IDENTIFICATION
12  * src/backend/nodes/read.c
13  *
14  * HISTORY
15  * AUTHOR DATE MAJOR EVENT
16  * Andrew Yu Nov 2, 1994 file creation
17  *
18  *-------------------------------------------------------------------------
19  */
20 #include "postgres.h"
21 
22 #include <ctype.h>
23 
24 #include "nodes/pg_list.h"
25 #include "nodes/readfuncs.h"
26 #include "nodes/value.h"
27 
28 
29 /* Static state for pg_strtok */
30 static char *pg_strtok_ptr = NULL;
31 
32 
33 /*
34  * stringToNode -
35  * returns a Node with a given legal ASCII representation
36  */
37 void *
38 stringToNode(char *str)
39 {
40  char *save_strtok;
41  void *retval;
42 
43  /*
44  * We save and restore the pre-existing state of pg_strtok. This makes the
45  * world safe for re-entrant invocation of stringToNode, without incurring
46  * a lot of notational overhead by having to pass the next-character
47  * pointer around through all the readfuncs.c code.
48  */
49  save_strtok = pg_strtok_ptr;
50 
51  pg_strtok_ptr = str; /* point pg_strtok at the string to read */
52 
53  retval = nodeRead(NULL, 0); /* do the reading */
54 
55  pg_strtok_ptr = save_strtok;
56 
57  return retval;
58 }
59 
60 /*****************************************************************************
61  *
62  * the lisp token parser
63  *
64  *****************************************************************************/
65 
66 /*
67  * pg_strtok --- retrieve next "token" from a string.
68  *
69  * Works kinda like strtok, except it never modifies the source string.
70  * (Instead of storing nulls into the string, the length of the token
71  * is returned to the caller.)
72  * Also, the rules about what is a token are hard-wired rather than being
73  * configured by passing a set of terminating characters.
74  *
75  * The string is assumed to have been initialized already by stringToNode.
76  *
77  * The rules for tokens are:
78  * * Whitespace (space, tab, newline) always separates tokens.
79  * * The characters '(', ')', '{', '}' form individual tokens even
80  * without any whitespace around them.
81  * * Otherwise, a token is all the characters up to the next whitespace
82  * or occurrence of one of the four special characters.
83  * * A backslash '\' can be used to quote whitespace or one of the four
84  * special characters, so that it is treated as a plain token character.
85  * Backslashes themselves must also be backslashed for consistency.
86  * Any other character can be, but need not be, backslashed as well.
87  * * If the resulting token is '<>' (with no backslash), it is returned
88  * as a non-NULL pointer to the token but with length == 0. Note that
89  * there is no other way to get a zero-length token.
90  *
91  * Returns a pointer to the start of the next token, and the length of the
92  * token (including any embedded backslashes!) in *length. If there are
93  * no more tokens, NULL and 0 are returned.
94  *
95  * NOTE: this routine doesn't remove backslashes; the caller must do so
96  * if necessary (see "debackslash").
97  *
98  * NOTE: prior to release 7.0, this routine also had a special case to treat
99  * a token starting with '"' as extending to the next '"'. This code was
100  * broken, however, since it would fail to cope with a string containing an
101  * embedded '"'. I have therefore removed this special case, and instead
102  * introduced rules for using backslashes to quote characters. Higher-level
103  * code should add backslashes to a string constant to ensure it is treated
104  * as a single token.
105  */
106 char *
108 {
109  char *local_str; /* working pointer to string */
110  char *ret_str; /* start of token to return */
111 
112  local_str = pg_strtok_ptr;
113 
114  while (*local_str == ' ' || *local_str == '\n' || *local_str == '\t')
115  local_str++;
116 
117  if (*local_str == '\0')
118  {
119  *length = 0;
120  pg_strtok_ptr = local_str;
121  return NULL; /* no more tokens */
122  }
123 
124  /*
125  * Now pointing at start of next token.
126  */
127  ret_str = local_str;
128 
129  if (*local_str == '(' || *local_str == ')' ||
130  *local_str == '{' || *local_str == '}')
131  {
132  /* special 1-character token */
133  local_str++;
134  }
135  else
136  {
137  /* Normal token, possibly containing backslashes */
138  while (*local_str != '\0' &&
139  *local_str != ' ' && *local_str != '\n' &&
140  *local_str != '\t' &&
141  *local_str != '(' && *local_str != ')' &&
142  *local_str != '{' && *local_str != '}')
143  {
144  if (*local_str == '\\' && local_str[1] != '\0')
145  local_str += 2;
146  else
147  local_str++;
148  }
149  }
150 
151  *length = local_str - ret_str;
152 
153  /* Recognize special case for "empty" token */
154  if (*length == 2 && ret_str[0] == '<' && ret_str[1] == '>')
155  *length = 0;
156 
157  pg_strtok_ptr = local_str;
158 
159  return ret_str;
160 }
161 
162 /*
163  * debackslash -
164  * create a palloc'd string holding the given token.
165  * any protective backslashes in the token are removed.
166  */
167 char *
168 debackslash(char *token, int length)
169 {
170  char *result = palloc(length + 1);
171  char *ptr = result;
172 
173  while (length > 0)
174  {
175  if (*token == '\\' && length > 1)
176  token++, length--;
177  *ptr++ = *token++;
178  length--;
179  }
180  *ptr = '\0';
181  return result;
182 }
183 
184 #define RIGHT_PAREN (1000000 + 1)
185 #define LEFT_PAREN (1000000 + 2)
186 #define LEFT_BRACE (1000000 + 3)
187 #define OTHER_TOKEN (1000000 + 4)
188 
189 /*
190  * nodeTokenType -
191  * returns the type of the node token contained in token.
192  * It returns one of the following valid NodeTags:
193  * T_Integer, T_Float, T_String, T_BitString
194  * and some of its own:
195  * RIGHT_PAREN, LEFT_PAREN, LEFT_BRACE, OTHER_TOKEN
196  *
197  * Assumption: the ascii representation is legal
198  */
199 static NodeTag
200 nodeTokenType(char *token, int length)
201 {
202  NodeTag retval;
203  char *numptr;
204  int numlen;
205 
206  /*
207  * Check if the token is a number
208  */
209  numptr = token;
210  numlen = length;
211  if (*numptr == '+' || *numptr == '-')
212  numptr++, numlen--;
213  if ((numlen > 0 && isdigit((unsigned char) *numptr)) ||
214  (numlen > 1 && *numptr == '.' && isdigit((unsigned char) numptr[1])))
215  {
216  /*
217  * Yes. Figure out whether it is integral or float; this requires
218  * both a syntax check and a range check. strtol() can do both for us.
219  * We know the token will end at a character that strtol will stop at,
220  * so we do not need to modify the string.
221  */
222  long val;
223  char *endptr;
224 
225  errno = 0;
226  val = strtol(token, &endptr, 10);
227  (void) val; /* avoid compiler warning if unused */
228  if (endptr != token + length || errno == ERANGE
229 #ifdef HAVE_LONG_INT_64
230  /* if long > 32 bits, check for overflow of int4 */
231  || val != (long) ((int32) val)
232 #endif
233  )
234  return T_Float;
235  return T_Integer;
236  }
237 
238  /*
239  * these three cases do not need length checks, since pg_strtok() will
240  * always treat them as single-byte tokens
241  */
242  else if (*token == '(')
243  retval = LEFT_PAREN;
244  else if (*token == ')')
245  retval = RIGHT_PAREN;
246  else if (*token == '{')
247  retval = LEFT_BRACE;
248  else if (*token == '"' && length > 1 && token[length - 1] == '"')
249  retval = T_String;
250  else if (*token == 'b')
251  retval = T_BitString;
252  else
253  retval = OTHER_TOKEN;
254  return retval;
255 }
256 
257 /*
258  * nodeRead -
259  * Slightly higher-level reader.
260  *
261  * This routine applies some semantic knowledge on top of the purely
262  * lexical tokenizer pg_strtok(). It can read
263  * * Value token nodes (integers, floats, or strings);
264  * * General nodes (via parseNodeString() from readfuncs.c);
265  * * Lists of the above;
266  * * Lists of integers or OIDs.
267  * The return value is declared void *, not Node *, to avoid having to
268  * cast it explicitly in callers that assign to fields of different types.
269  *
270  * External callers should always pass NULL/0 for the arguments. Internally
271  * a non-NULL token may be passed when the upper recursion level has already
272  * scanned the first token of a node's representation.
273  *
274  * We assume pg_strtok is already initialized with a string to read (hence
275  * this should only be invoked from within a stringToNode operation).
276  */
277 void *
278 nodeRead(char *token, int tok_len)
279 {
280  Node *result;
281  NodeTag type;
282 
283  if (token == NULL) /* need to read a token? */
284  {
285  token = pg_strtok(&tok_len);
286 
287  if (token == NULL) /* end of input */
288  return NULL;
289  }
290 
291  type = nodeTokenType(token, tok_len);
292 
293  switch ((int) type)
294  {
295  case LEFT_BRACE:
296  result = parseNodeString();
297  token = pg_strtok(&tok_len);
298  if (token == NULL || token[0] != '}')
299  elog(ERROR, "did not find '}' at end of input node");
300  break;
301  case LEFT_PAREN:
302  {
303  List *l = NIL;
304 
305  /*----------
306  * Could be an integer list: (i int int ...)
307  * or an OID list: (o int int ...)
308  * or a list of nodes/values: (node node ...)
309  *----------
310  */
311  token = pg_strtok(&tok_len);
312  if (token == NULL)
313  elog(ERROR, "unterminated List structure");
314  if (tok_len == 1 && token[0] == 'i')
315  {
316  /* List of integers */
317  for (;;)
318  {
319  int val;
320  char *endptr;
321 
322  token = pg_strtok(&tok_len);
323  if (token == NULL)
324  elog(ERROR, "unterminated List structure");
325  if (token[0] == ')')
326  break;
327  val = (int) strtol(token, &endptr, 10);
328  if (endptr != token + tok_len)
329  elog(ERROR, "unrecognized integer: \"%.*s\"",
330  tok_len, token);
331  l = lappend_int(l, val);
332  }
333  }
334  else if (tok_len == 1 && token[0] == 'o')
335  {
336  /* List of OIDs */
337  for (;;)
338  {
339  Oid val;
340  char *endptr;
341 
342  token = pg_strtok(&tok_len);
343  if (token == NULL)
344  elog(ERROR, "unterminated List structure");
345  if (token[0] == ')')
346  break;
347  val = (Oid) strtoul(token, &endptr, 10);
348  if (endptr != token + tok_len)
349  elog(ERROR, "unrecognized OID: \"%.*s\"",
350  tok_len, token);
351  l = lappend_oid(l, val);
352  }
353  }
354  else
355  {
356  /* List of other node types */
357  for (;;)
358  {
359  /* We have already scanned next token... */
360  if (token[0] == ')')
361  break;
362  l = lappend(l, nodeRead(token, tok_len));
363  token = pg_strtok(&tok_len);
364  if (token == NULL)
365  elog(ERROR, "unterminated List structure");
366  }
367  }
368  result = (Node *) l;
369  break;
370  }
371  case RIGHT_PAREN:
372  elog(ERROR, "unexpected right parenthesis");
373  result = NULL; /* keep compiler happy */
374  break;
375  case OTHER_TOKEN:
376  if (tok_len == 0)
377  {
378  /* must be "<>" --- represents a null pointer */
379  result = NULL;
380  }
381  else
382  {
383  elog(ERROR, "unrecognized token: \"%.*s\"", tok_len, token);
384  result = NULL; /* keep compiler happy */
385  }
386  break;
387  case T_Integer:
388 
389  /*
390  * we know that the token terminates on a char atol will stop at
391  */
392  result = (Node *) makeInteger(atol(token));
393  break;
394  case T_Float:
395  {
396  char *fval = (char *) palloc(tok_len + 1);
397 
398  memcpy(fval, token, tok_len);
399  fval[tok_len] = '\0';
400  result = (Node *) makeFloat(fval);
401  }
402  break;
403  case T_String:
404  /* need to remove leading and trailing quotes, and backslashes */
405  result = (Node *) makeString(debackslash(token + 1, tok_len - 2));
406  break;
407  case T_BitString:
408  {
409  char *val = palloc(tok_len);
410 
411  /* skip leading 'b' */
412  memcpy(val, token + 1, tok_len - 1);
413  val[tok_len - 1] = '\0';
414  result = (Node *) makeBitString(val);
415  break;
416  }
417  default:
418  elog(ERROR, "unrecognized node type: %d", (int) type);
419  result = NULL; /* keep compiler happy */
420  break;
421  }
422 
423  return (void *) result;
424 }
Value * makeString(char *str)
Definition: value.c:53
#define NIL
Definition: pg_list.h:69
int length(const List *list)
Definition: list.c:1271
void * stringToNode(char *str)
Definition: read.c:38
char * pg_strtok(int *length)
Definition: read.c:107
Definition: nodes.h:509
return result
Definition: formatting.c:1633
void * nodeRead(char *token, int tok_len)
Definition: read.c:278
unsigned int Oid
Definition: postgres_ext.h:31
NodeTag
Definition: nodes.h:26
List * lappend_oid(List *list, Oid datum)
Definition: list.c:164
signed int int32
Definition: c.h:256
static NodeTag nodeTokenType(char *token, int length)
Definition: read.c:200
Value * makeInteger(long i)
Definition: value.c:23
#define ERROR
Definition: elog.h:43
#define RIGHT_PAREN
Definition: read.c:184
Value * makeBitString(char *str)
Definition: value.c:68
char * debackslash(char *token, int length)
Definition: read.c:168
List * lappend_int(List *list, int datum)
Definition: list.c:146
List * lappend(List *list, void *datum)
Definition: list.c:128
Value * makeFloat(char *numericStr)
Definition: value.c:38
#define LEFT_BRACE
Definition: read.c:186
static char * pg_strtok_ptr
Definition: read.c:30
#define NULL
Definition: c.h:229
Node * parseNodeString(void)
Definition: readfuncs.c:2408
Definition: nodes.h:283
void * palloc(Size size)
Definition: mcxt.c:849
#define elog
Definition: elog.h:219
#define OTHER_TOKEN
Definition: read.c:187
Definition: pg_list.h:45
long val
Definition: informix.c:689
#define LEFT_PAREN
Definition: read.c:185