LLVM 19.0.0git
LEB128.h
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1//===- llvm/Support/LEB128.h - [SU]LEB128 utility functions -----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file declares some utility functions for encoding SLEB128 and
10// ULEB128 values.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_SUPPORT_LEB128_H
15#define LLVM_SUPPORT_LEB128_H
16
18
19namespace llvm {
20
21/// Utility function to encode a SLEB128 value to an output stream. Returns
22/// the length in bytes of the encoded value.
23inline unsigned encodeSLEB128(int64_t Value, raw_ostream &OS,
24 unsigned PadTo = 0) {
25 bool More;
26 unsigned Count = 0;
27 do {
28 uint8_t Byte = Value & 0x7f;
29 // NOTE: this assumes that this signed shift is an arithmetic right shift.
30 Value >>= 7;
31 More = !((((Value == 0 ) && ((Byte & 0x40) == 0)) ||
32 ((Value == -1) && ((Byte & 0x40) != 0))));
33 Count++;
34 if (More || Count < PadTo)
35 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
36 OS << char(Byte);
37 } while (More);
38
39 // Pad with 0x80 and emit a terminating byte at the end.
40 if (Count < PadTo) {
41 uint8_t PadValue = Value < 0 ? 0x7f : 0x00;
42 for (; Count < PadTo - 1; ++Count)
43 OS << char(PadValue | 0x80);
44 OS << char(PadValue);
45 Count++;
46 }
47 return Count;
48}
49
50/// Utility function to encode a SLEB128 value to a buffer. Returns
51/// the length in bytes of the encoded value.
52inline unsigned encodeSLEB128(int64_t Value, uint8_t *p, unsigned PadTo = 0) {
53 uint8_t *orig_p = p;
54 unsigned Count = 0;
55 bool More;
56 do {
57 uint8_t Byte = Value & 0x7f;
58 // NOTE: this assumes that this signed shift is an arithmetic right shift.
59 Value >>= 7;
60 More = !((((Value == 0 ) && ((Byte & 0x40) == 0)) ||
61 ((Value == -1) && ((Byte & 0x40) != 0))));
62 Count++;
63 if (More || Count < PadTo)
64 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
65 *p++ = Byte;
66 } while (More);
67
68 // Pad with 0x80 and emit a terminating byte at the end.
69 if (Count < PadTo) {
70 uint8_t PadValue = Value < 0 ? 0x7f : 0x00;
71 for (; Count < PadTo - 1; ++Count)
72 *p++ = (PadValue | 0x80);
73 *p++ = PadValue;
74 }
75 return (unsigned)(p - orig_p);
76}
77
78/// Utility function to encode a ULEB128 value to an output stream. Returns
79/// the length in bytes of the encoded value.
81 unsigned PadTo = 0) {
82 unsigned Count = 0;
83 do {
84 uint8_t Byte = Value & 0x7f;
85 Value >>= 7;
86 Count++;
87 if (Value != 0 || Count < PadTo)
88 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
89 OS << char(Byte);
90 } while (Value != 0);
91
92 // Pad with 0x80 and emit a null byte at the end.
93 if (Count < PadTo) {
94 for (; Count < PadTo - 1; ++Count)
95 OS << '\x80';
96 OS << '\x00';
97 Count++;
98 }
99 return Count;
100}
101
102/// Utility function to encode a ULEB128 value to a buffer. Returns
103/// the length in bytes of the encoded value.
104inline unsigned encodeULEB128(uint64_t Value, uint8_t *p,
105 unsigned PadTo = 0) {
106 uint8_t *orig_p = p;
107 unsigned Count = 0;
108 do {
109 uint8_t Byte = Value & 0x7f;
110 Value >>= 7;
111 Count++;
112 if (Value != 0 || Count < PadTo)
113 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
114 *p++ = Byte;
115 } while (Value != 0);
116
117 // Pad with 0x80 and emit a null byte at the end.
118 if (Count < PadTo) {
119 for (; Count < PadTo - 1; ++Count)
120 *p++ = '\x80';
121 *p++ = '\x00';
122 }
123
124 return (unsigned)(p - orig_p);
125}
126
127/// Utility function to decode a ULEB128 value.
128///
129/// If \p error is non-null, it will point to a static error message,
130/// if an error occured. It will not be modified on success.
131inline uint64_t decodeULEB128(const uint8_t *p, unsigned *n = nullptr,
132 const uint8_t *end = nullptr,
133 const char **error = nullptr) {
134 const uint8_t *orig_p = p;
135 uint64_t Value = 0;
136 unsigned Shift = 0;
137 do {
138 if (LLVM_UNLIKELY(p == end)) {
139 if (error)
140 *error = "malformed uleb128, extends past end";
141 Value = 0;
142 break;
143 }
144 uint64_t Slice = *p & 0x7f;
145 if (LLVM_UNLIKELY(Shift >= 63) &&
146 ((Shift == 63 && (Slice << Shift >> Shift) != Slice) ||
147 (Shift > 63 && Slice != 0))) {
148 if (error)
149 *error = "uleb128 too big for uint64";
150 Value = 0;
151 break;
152 }
153 Value += Slice << Shift;
154 Shift += 7;
155 } while (*p++ >= 128);
156 if (n)
157 *n = (unsigned)(p - orig_p);
158 return Value;
159}
160
161/// Utility function to decode a SLEB128 value.
162///
163/// If \p error is non-null, it will point to a static error message,
164/// if an error occured. It will not be modified on success.
165inline int64_t decodeSLEB128(const uint8_t *p, unsigned *n = nullptr,
166 const uint8_t *end = nullptr,
167 const char **error = nullptr) {
168 const uint8_t *orig_p = p;
169 int64_t Value = 0;
170 unsigned Shift = 0;
171 uint8_t Byte;
172 do {
173 if (LLVM_UNLIKELY(p == end)) {
174 if (error)
175 *error = "malformed sleb128, extends past end";
176 if (n)
177 *n = (unsigned)(p - orig_p);
178 return 0;
179 }
180 Byte = *p;
181 uint64_t Slice = Byte & 0x7f;
182 if (LLVM_UNLIKELY(Shift >= 63) &&
183 ((Shift == 63 && Slice != 0 && Slice != 0x7f) ||
184 (Shift > 63 && Slice != (Value < 0 ? 0x7f : 0x00)))) {
185 if (error)
186 *error = "sleb128 too big for int64";
187 if (n)
188 *n = (unsigned)(p - orig_p);
189 return 0;
190 }
191 Value |= Slice << Shift;
192 Shift += 7;
193 ++p;
194 } while (Byte >= 128);
195 // Sign extend negative numbers if needed.
196 if (Shift < 64 && (Byte & 0x40))
197 Value |= UINT64_MAX << Shift;
198 if (n)
199 *n = (unsigned)(p - orig_p);
200 return Value;
201}
202
203/// Utility function to get the size of the ULEB128-encoded value.
204extern unsigned getULEB128Size(uint64_t Value);
205
206/// Utility function to get the size of the SLEB128-encoded value.
207extern unsigned getSLEB128Size(int64_t Value);
208
209} // namespace llvm
210
211#endif // LLVM_SUPPORT_LEB128_H
#define LLVM_UNLIKELY(EXPR)
Definition: Compiler.h:241
raw_pwrite_stream & OS
#define error(X)
LLVM Value Representation.
Definition: Value.h:74
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
#define UINT64_MAX
Definition: DataTypes.h:77
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
uint64_t decodeULEB128(const uint8_t *p, unsigned *n=nullptr, const uint8_t *end=nullptr, const char **error=nullptr)
Utility function to decode a ULEB128 value.
Definition: LEB128.h:131
int64_t decodeSLEB128(const uint8_t *p, unsigned *n=nullptr, const uint8_t *end=nullptr, const char **error=nullptr)
Utility function to decode a SLEB128 value.
Definition: LEB128.h:165
unsigned getULEB128Size(uint64_t Value)
Utility function to get the size of the ULEB128-encoded value.
Definition: LEB128.cpp:19
unsigned encodeSLEB128(int64_t Value, raw_ostream &OS, unsigned PadTo=0)
Utility function to encode a SLEB128 value to an output stream.
Definition: LEB128.h:23
unsigned encodeULEB128(uint64_t Value, raw_ostream &OS, unsigned PadTo=0)
Utility function to encode a ULEB128 value to an output stream.
Definition: LEB128.h:80
unsigned getSLEB128Size(int64_t Value)
Utility function to get the size of the SLEB128-encoded value.
Definition: LEB128.cpp:29