1 /** @file
2 
3   This file implements an abstract class to map between numbers of type IntType
4 
5   @section license License
6 
7   Licensed to the Apache Software Foundation (ASF) under one
8   or more contributor license agreements.  See the NOTICE file
9   distributed with this work for additional information
10   regarding copyright ownership.  The ASF licenses this file
11   to you under the Apache License, Version 2.0 (the
12   "License"); you may not use this file except in compliance
13   with the License.  You may obtain a copy of the License at
14 
15       http://www.apache.org/licenses/LICENSE-2.0
16 
17   Unless required by applicable law or agreed to in writing, software
18   distributed under the License is distributed on an "AS IS" BASIS,
19   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
20   See the License for the specific language governing permissions and
21   limitations under the License.
22 
23   @section description
24   This file implements an abstract class to map between numbers of type IntType
25   and strings. The purpose is to obtain one representation from the other so that
26   easily remembered names can be used to refer to log fields of integer type.
27  */
28 
29 #pragma once
30 
31 #include <cstdarg>
32 #include <cstring>
33 
34 #include "tscore/ink_platform.h"
35 #include "tscore/Ptr.h"
36 #include "LogUtils.h"
37 #include "tscore/ink_string.h"
38 
39 /*****************************************************************************
40 
41 The LogFieldAliasMap class is an abstract class used to provide an
42 interface to map between numbers of type IntType and strings. The
43 purpose is to obtain one representation from the other so that easy to
44 remember names can be used to refer to log fields of integer type.
45 
46 The methods that subclasses should implement are:
47 
48 1) asInt(char *key, IntType *val)
49 
50 This method takes a string and sets the IntType argument to the
51 corresponding value, (unless the string is invalid). It returns an
52 error status.
53 
54 2) asString(IntType key, char *buf, size_t bufLen, size_t *numChars=0)
55 
56 This method takes an IntType key and writes its equivalent string to a
57 buffer buf of length bufLen. It sets the number of written characters
58 numChars (if numChars is not NULL), and returns an error status.
59 
60 The IntType to string conversion is used when unmarshaling data prior to
61 writing to a log file, and the string to IntType conversion is used when
62 building filters (so that the filter value can be specified as a string,
63 but the actual field comparison is done between IntTypes).
64 
65 Note that LogFieldAliasMap is derived from RefCountObj, so once a map
66 is constructed a pointer to it can be passed to other objects (e.g.,
67 to a LogField object) without the object having to worry about freeing
68 any memory the map may have allocated.
69 
70  *****************************************************************************/
71 
72 class LogFieldAliasMap : public RefCountObj
73 {
74 public:
75   // the logging system assumes log entries of type sINT are
76   // unsigned (signed?) integers (int64_t type) so we define IntType
77   // to be unsigned (signed?)
78   // The problem using the correct type is that the init method is
79   // vararg. To make that work, we must use the "generic" int.
80 
81   typedef int64_t IntType;
82   enum {
83     ALL_OK = 0,
84     INVALID_INT,
85     INVALID_STRING,
86     BUFFER_TOO_SMALL,
87   };
88 
89   virtual int asInt(char *key, IntType *val, bool case_sensitive = false) const                 = 0;
90   virtual int asString(IntType key, char *buf, size_t bufLen, size_t *numChars = nullptr) const = 0;
91 };
92 
93 /*****************************************************************************
94 
95 A LogFieldAliasTable implements a LogFieldAliasMap through a
96 straightforward table. The entries in the table are input with the
97 init(numPairs, ...) method.  Arguments to this method are the number
98 numPairs of table entries, followed by the entries themselves in the
99 form integer, string. For example:
100 
101 table->init(3, 1, "one", 2, "two", 7, "seven")
102 
103  *****************************************************************************/
104 
105 struct LogFieldAliasTableEntry {
106   bool valid    = false;   // entry in table is valid
107   char *name    = nullptr; // the string equivalent
108   size_t length = 0;       // the length of the string
109 
LogFieldAliasTableEntryLogFieldAliasTableEntry110   LogFieldAliasTableEntry() {}
~LogFieldAliasTableEntryLogFieldAliasTableEntry111   ~LogFieldAliasTableEntry()
112   {
113     if (name) {
114       free(name);
115     }
116   }
117 };
118 
119 class LogFieldAliasTable : public LogFieldAliasMap
120 {
121 private:
122   IntType m_min                    = 0;       // minimum numeric value
123   IntType m_max                    = 0;       // maximum numeric value
124   IntType m_entries                = 0;       // number of entries in table
125   LogFieldAliasTableEntry *m_table = nullptr; // array of table entries
126 
127 public:
LogFieldAliasTable()128   LogFieldAliasTable() {}
~LogFieldAliasTable()129   ~LogFieldAliasTable() override { delete[] m_table; }
130   void init(size_t numPairs, ...);
131 
132   int
asInt(char * key,IntType * val,bool case_sensitive)133   asInt(char *key, IntType *val, bool case_sensitive) const override
134   {
135     int retVal = INVALID_STRING;
136 
137     for (IntType i = 0; i < m_entries; i++) {
138       bool found;
139       if (m_table[i].valid) {
140         if (case_sensitive) {
141           found = (strcmp(key, m_table[i].name) == 0);
142         } else {
143           found = (strcasecmp(key, m_table[i].name) == 0);
144         }
145       } else {
146         found = false;
147       }
148       if (found) {
149         *val   = (unsigned int)(i + m_min);
150         retVal = ALL_OK;
151         break;
152       }
153     }
154 
155     return retVal;
156   }
157 
158   int
159   asString(IntType key, char *buf, size_t bufLen, size_t *numCharsPtr = nullptr) const override
160   {
161     int retVal;
162     size_t numChars;
163 
164     size_t i = key - m_min;
165     if (m_entries && key >= m_min && key <= m_max && m_table[i].valid) {
166       size_t l = m_table[i].length;
167       if (l < bufLen) {
168         ink_strlcpy(buf, m_table[key - m_min].name, bufLen);
169         numChars = l;
170         retVal   = ALL_OK;
171       } else {
172         numChars = 0;
173         retVal   = BUFFER_TOO_SMALL;
174       }
175     } else {
176       numChars = 0;
177       retVal   = INVALID_INT;
178     }
179     if (numCharsPtr) {
180       *numCharsPtr = numChars;
181     }
182     return retVal;
183   }
184 };
185 
186 // LOG_FIELD_ALIAS_MAP_H
187