value.h revision 000e31195ad4ad30a0c80c93ab57a424e7d8d918 
1/*
2 * This file is part of ltrace.
3 * Copyright (C) 2011,2012 Petr Machata, Red Hat Inc.
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
7 * published by the Free Software Foundation; either version 2 of the
8 * License, or (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
18 * 02110-1301 USA
19 */
20
21#ifndef VALUE_H
22#define VALUE_H
23
24#include "forward.h"
25
26/* Values are objects that capture data fetched from an inferior.
27 * Typically a value is attached to a single inferior where it was
28 * extracted from, but it is possible to create a detached value.
29 * Each value is typed.  Values support a number of routines, such as
30 * dereferencing if the value is of pointer type, array or structure
31 * access, etc.
32 *
33 * A value can be uninitialized, abstract or reified.  Abstract values
34 * are just references into inferior, no transfer has taken place yet.
35 * Reified values have been copied out of the corresponding inferior,
36 * or otherwise set to some value.  */
37
38enum value_location_t {
39	VAL_LOC_NODATA = 0,	/* Uninitialized.  */
40	VAL_LOC_INFERIOR,	/* Value is in the inferior process.  */
41	VAL_LOC_COPY,		/* Value was copied out of the inferior.  */
42	VAL_LOC_SHARED,		/* Like VAL_LOC_COPY, but don't free.  */
43	VAL_LOC_WORD,		/* Like VAL_LOC_COPY, but small enough.  */
44};
45
46struct value {
47	struct arg_type_info *type;
48	struct Process *inferior;
49	struct value *parent;
50	size_t size;
51	union {
52		void *address;  /* VAL_LOC_CLIENT, VAL_LOC_COPY,
53				   VAL_LOC_SHARED */
54		long value;     /* VAL_LOC_WORD */
55		unsigned char buf[0];
56	} u;
57	enum value_location_t where;
58	int own_type;
59};
60
61/* Initialize VALUE.  INFERIOR must not be NULL.  PARENT is parental
62 * value, in case of compound types.  It may be NULL.  TYPE is a type
63 * of the value.  It may be NULL if the type is not yet known.  If
64 * OWN_TYPE, the passed-in type is owned and released by value.  */
65void value_init(struct value *value, struct Process *inferior,
66		struct value *parent, struct arg_type_info *type,
67		int own_type);
68
69/* Initialize VALUE.  This is like value_init, except that inferior is
70 * NULL.  VALP is initialized as a detached value, without assigned
71 * process.  You have to be careful not to use VAL_LOC_INFERIOR
72 * values if the value is detached.  */
73void value_init_detached(struct value *value, struct value *parent,
74			 struct arg_type_info *type, int own_type);
75
76/* Set TYPE.  This releases old type if it was owned.  TYPE is owned
77 * and released if OWN_TYPE.  */
78void value_set_type(struct value *value,
79		    struct arg_type_info *type, int own_type);
80
81/* Transfers the ownership of VALUE's type, if any, to the caller.
82 * This doesn't reset the VALUE's type, but gives up ownership if
83 * there was one.  Previous ownership is passed in OWN_TYPE.  */
84void value_take_type(struct value *value,
85		     struct arg_type_info **type, int *own_type);
86
87/* Release the data held by VALP, if any, but not the type.  */
88void value_release(struct value *valp);
89
90/* Destroy the value.  This is like value_release, but it additionally
91 * frees the value type, if it's own_type.  It doesn't free the VAL
92 * pointer itself.  */
93void value_destroy(struct value *val);
94
95/* Set the data held by VALP to VALUE.  This also sets the value's
96 * where to VAL_LOC_WORD.  */
97void value_set_long(struct value *valp, long value);
98
99/* Set the data held by VALP to a buffer of size SIZE.  This buffer
100 * may be allocated by malloc.  Returns NULL on failure.  */
101unsigned char *value_reserve(struct value *valp, size_t size);
102
103/* Access ELEMENT-th field of the compound value VALP, and store the
104 * result into the value RET_VAL.  Returns 0 on success, or negative
105 * value on failure.  */
106int value_init_element(struct value *ret_val, struct value *valp, size_t element);
107
108/* De-reference pointer value, and store the result into the value
109 * RET_VAL.  Returns 0 on success, or negative value on failure.  */
110int value_init_deref(struct value *ret_val, struct value *valp);
111
112/* If value is in inferior, copy it over to ltrace.  Return 0 for
113 * success or negative value for failure.  */
114int value_reify(struct value *val, struct value_dict *arguments);
115
116/* Return a pointer to the data of the value.  This copies the data
117 * from the inferior to the tracer.  Returns NULL on failure.  */
118unsigned char *value_get_data(struct value *val, struct value_dict *arguments);
119
120/* Return a pointer to the raw data of the value.  This shall not be
121 * called on a VAL_LOC_INFERIOR value.  */
122unsigned char *value_get_raw_data(struct value *val);
123
124/* Copy value VAL into the area pointed-to by RETP.  Return 0 on
125 * success or a negative value on failure.  */
126int value_clone(struct value *retp, struct value *val);
127
128/* Give a size of given value.  Return (size_t)-1 for error.  This is
129 * a full size of the value.  In particular for arrays, it returns
130 * actual length of the array, as computed by the length
131 * expression.  */
132size_t value_size(struct value *val, struct value_dict *arguments);
133
134/* Extract at most word-sized datum from the value.  Return 0 on
135 * success or negative value on failure.  */
136int value_extract_word(struct value *val, long *retp,
137		       struct value_dict *arguments);
138
139/* Copy contents of VAL to DATA.  The buffer must be large enough to
140 * hold all the data inside.  */
141int value_extract_buf(struct value *val, unsigned char *data,
142		      struct value_dict *arguments);
143
144/* Find the most enclosing parental value that is a struct.  Return
145 * NULL when there is no such parental value.  */
146struct value *value_get_parental_struct(struct value *val);
147
148/* Determine whether this is all-zero value.  Returns >0 if it is, ==0
149 * if it isn't, <0 on error.  */
150int value_is_zero(struct value *val, struct value_dict *arguments);
151
152#endif /* VALUE_H */
153