1//===-- MappedHash.h --------------------------------------------*- 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#ifndef liblldb_MappedHash_h_ 10#define liblldb_MappedHash_h_ 11 12#include <assert.h> 13#include <stdint.h> 14 15#include <algorithm> 16#include <functional> 17#include <map> 18#include <vector> 19 20#include "lldb/Utility/DataExtractor.h" 21#include "lldb/Utility/Stream.h" 22#include "llvm/Support/DJB.h" 23 24class MappedHash { 25public: 26 enum HashFunctionType { 27 eHashFunctionDJB = 0u // Daniel J Bernstein hash function that is also used 28 // by the ELF GNU_HASH sections 29 }; 30 31 static uint32_t HashString(uint32_t hash_function, llvm::StringRef s) { 32 switch (hash_function) { 33 case MappedHash::eHashFunctionDJB: 34 return llvm::djbHash(s); 35 36 default: 37 break; 38 } 39 llvm_unreachable("Invalid hash function index"); 40 } 41 42 static const uint32_t HASH_MAGIC = 0x48415348u; 43 static const uint32_t HASH_CIGAM = 0x48534148u; 44 45 template <typename T> struct Header { 46 typedef T HeaderData; 47 48 uint32_t 49 magic; // HASH_MAGIC or HASH_CIGAM magic value to allow endian detection 50 uint16_t version; // Version number 51 uint16_t hash_function; // The hash function enumeration that was used 52 uint32_t bucket_count; // The number of buckets in this hash table 53 uint32_t hashes_count; // The total number of unique hash values and hash 54 // data offsets in this table 55 uint32_t header_data_len; // The size in bytes of the "header_data" template 56 // member below 57 HeaderData header_data; // 58 59 Header() 60 : magic(HASH_MAGIC), version(1), hash_function(eHashFunctionDJB), 61 bucket_count(0), hashes_count(0), header_data_len(sizeof(T)), 62 header_data() {} 63 64 virtual ~Header() = default; 65 66 size_t GetByteSize() const { 67 return sizeof(magic) + sizeof(version) + sizeof(hash_function) + 68 sizeof(bucket_count) + sizeof(hashes_count) + 69 sizeof(header_data_len) + header_data_len; 70 } 71 72 virtual size_t GetByteSize(const HeaderData &header_data) = 0; 73 74 void SetHeaderDataByteSize(uint32_t header_data_byte_size) { 75 header_data_len = header_data_byte_size; 76 } 77 78 void Dump(lldb_private::Stream &s) { 79 s.Printf("header.magic = 0x%8.8x\n", magic); 80 s.Printf("header.version = 0x%4.4x\n", version); 81 s.Printf("header.hash_function = 0x%4.4x\n", hash_function); 82 s.Printf("header.bucket_count = 0x%8.8x %u\n", bucket_count, 83 bucket_count); 84 s.Printf("header.hashes_count = 0x%8.8x %u\n", hashes_count, 85 hashes_count); 86 s.Printf("header.header_data_len = 0x%8.8x %u\n", header_data_len, 87 header_data_len); 88 } 89 90 virtual lldb::offset_t Read(lldb_private::DataExtractor &data, 91 lldb::offset_t offset) { 92 if (data.ValidOffsetForDataOfSize( 93 offset, sizeof(magic) + sizeof(version) + sizeof(hash_function) + 94 sizeof(bucket_count) + sizeof(hashes_count) + 95 sizeof(header_data_len))) { 96 magic = data.GetU32(&offset); 97 if (magic != HASH_MAGIC) { 98 if (magic == HASH_CIGAM) { 99 switch (data.GetByteOrder()) { 100 case lldb::eByteOrderBig: 101 data.SetByteOrder(lldb::eByteOrderLittle); 102 break; 103 case lldb::eByteOrderLittle: 104 data.SetByteOrder(lldb::eByteOrderBig); 105 break; 106 default: 107 return LLDB_INVALID_OFFSET; 108 } 109 } else { 110 // Magic bytes didn't match 111 version = 0; 112 return LLDB_INVALID_OFFSET; 113 } 114 } 115 116 version = data.GetU16(&offset); 117 if (version != 1) { 118 // Unsupported version 119 return LLDB_INVALID_OFFSET; 120 } 121 hash_function = data.GetU16(&offset); 122 if (hash_function == 4) 123 hash_function = 0; // Deal with pre-release version of this table... 124 bucket_count = data.GetU32(&offset); 125 hashes_count = data.GetU32(&offset); 126 header_data_len = data.GetU32(&offset); 127 return offset; 128 } 129 return LLDB_INVALID_OFFSET; 130 } 131 // 132 // // Returns a buffer that contains a serialized version of this 133 // table 134 // // that must be freed with free(). 135 // virtual void * 136 // Write (int fd); 137 }; 138 139 // A class for reading and using a saved hash table from a block of data 140 // in memory 141 template <typename __KeyType, class __HeaderType, class __HashData> 142 class MemoryTable { 143 public: 144 typedef __HeaderType HeaderType; 145 typedef __KeyType KeyType; 146 typedef __HashData HashData; 147 148 enum Result { 149 eResultKeyMatch = 0u, // The entry was found, key matched and "pair" was 150 // filled in successfully 151 eResultKeyMismatch = 152 1u, // Bucket hash data collision, but key didn't match 153 eResultEndOfHashData = 2u, // The chain of items for this hash data in 154 // this bucket is terminated, search no more 155 eResultError = 3u // Status parsing the hash data, abort 156 }; 157 158 struct Pair { 159 KeyType key; 160 HashData value; 161 }; 162 163 MemoryTable(lldb_private::DataExtractor &data) 164 : m_header(), m_hash_indexes(nullptr), m_hash_values(nullptr), 165 m_hash_offsets(nullptr) { 166 lldb::offset_t offset = m_header.Read(data, 0); 167 if (offset != LLDB_INVALID_OFFSET && IsValid()) { 168 m_hash_indexes = (const uint32_t *)data.GetData( 169 &offset, m_header.bucket_count * sizeof(uint32_t)); 170 m_hash_values = (const uint32_t *)data.GetData( 171 &offset, m_header.hashes_count * sizeof(uint32_t)); 172 m_hash_offsets = (const uint32_t *)data.GetData( 173 &offset, m_header.hashes_count * sizeof(uint32_t)); 174 } 175 } 176 177 virtual ~MemoryTable() = default; 178 179 bool IsValid() const { 180 return m_header.version == 1 && 181 m_header.hash_function == eHashFunctionDJB && 182 m_header.bucket_count > 0; 183 } 184 185 uint32_t GetHashIndex(uint32_t bucket_idx) const { 186 uint32_t result = UINT32_MAX; 187 if (m_hash_indexes && bucket_idx < m_header.bucket_count) 188 memcpy(&result, m_hash_indexes + bucket_idx, sizeof(uint32_t)); 189 return result; 190 } 191 192 uint32_t GetHashValue(uint32_t hash_idx) const { 193 uint32_t result = UINT32_MAX; 194 if (m_hash_values && hash_idx < m_header.hashes_count) 195 memcpy(&result, m_hash_values + hash_idx, sizeof(uint32_t)); 196 return result; 197 } 198 199 uint32_t GetHashDataOffset(uint32_t hash_idx) const { 200 uint32_t result = UINT32_MAX; 201 if (m_hash_offsets && hash_idx < m_header.hashes_count) 202 memcpy(&result, m_hash_offsets + hash_idx, sizeof(uint32_t)); 203 return result; 204 } 205 206 bool Find(llvm::StringRef name, Pair &pair) const { 207 if (name.empty()) 208 return false; 209 210 if (IsValid()) { 211 const uint32_t bucket_count = m_header.bucket_count; 212 const uint32_t hash_count = m_header.hashes_count; 213 const uint32_t hash_value = 214 MappedHash::HashString(m_header.hash_function, name); 215 const uint32_t bucket_idx = hash_value % bucket_count; 216 uint32_t hash_idx = GetHashIndex(bucket_idx); 217 if (hash_idx < hash_count) { 218 for (; hash_idx < hash_count; ++hash_idx) { 219 const uint32_t curr_hash_value = GetHashValue(hash_idx); 220 if (curr_hash_value == hash_value) { 221 lldb::offset_t hash_data_offset = GetHashDataOffset(hash_idx); 222 while (hash_data_offset != UINT32_MAX) { 223 const lldb::offset_t prev_hash_data_offset = hash_data_offset; 224 Result hash_result = 225 GetHashDataForName(name, &hash_data_offset, pair); 226 // Check the result of getting our hash data 227 switch (hash_result) { 228 case eResultKeyMatch: 229 return true; 230 231 case eResultKeyMismatch: 232 if (prev_hash_data_offset == hash_data_offset) 233 return false; 234 break; 235 236 case eResultEndOfHashData: 237 // The last HashData for this key has been reached, stop 238 // searching 239 return false; 240 case eResultError: 241 // Status parsing the hash data, abort 242 return false; 243 } 244 } 245 } 246 if ((curr_hash_value % bucket_count) != bucket_idx) 247 break; 248 } 249 } 250 } 251 return false; 252 } 253 254 // This method must be implemented in any subclasses. The KeyType is user 255 // specified and must somehow result in a string value. For example, the 256 // KeyType might be a string offset in a string table and subclasses can 257 // store their string table as a member of the subclass and return a valie 258 // "const char *" given a "key". The value could also be a C string 259 // pointer, in which case just returning "key" will suffice. 260 virtual const char *GetStringForKeyType(KeyType key) const = 0; 261 262 virtual bool ReadHashData(uint32_t hash_data_offset, 263 HashData &hash_data) const = 0; 264 265 // This method must be implemented in any subclasses and it must try to 266 // read one "Pair" at the offset pointed to by the "hash_data_offset_ptr" 267 // parameter. This offset should be updated as bytes are consumed and a 268 // value "Result" enum should be returned. If the "name" matches the full 269 // name for the "pair.key" (which must be filled in by this call), then the 270 // HashData in the pair ("pair.value") should be extracted and filled in 271 // and "eResultKeyMatch" should be returned. If "name" doesn't match this 272 // string for the key, then "eResultKeyMismatch" should be returned and all 273 // data for the current HashData must be consumed or skipped and the 274 // "hash_data_offset_ptr" offset needs to be updated to point to the next 275 // HashData. If the end of the HashData objects for a given hash value have 276 // been reached, then "eResultEndOfHashData" should be returned. If 277 // anything else goes wrong during parsing, return "eResultError" and the 278 // corresponding "Find()" function will be canceled and return false. 279 virtual Result GetHashDataForName(llvm::StringRef name, 280 lldb::offset_t *hash_data_offset_ptr, 281 Pair &pair) const = 0; 282 283 const HeaderType &GetHeader() { return m_header; } 284 285 void ForEach( 286 std::function<bool(const HashData &hash_data)> const &callback) const { 287 const size_t num_hash_offsets = m_header.hashes_count; 288 for (size_t i = 0; i < num_hash_offsets; ++i) { 289 uint32_t hash_data_offset = GetHashDataOffset(i); 290 if (hash_data_offset != UINT32_MAX) { 291 HashData hash_data; 292 if (ReadHashData(hash_data_offset, hash_data)) { 293 // If the callback returns false, then we are done and should stop 294 if (callback(hash_data) == false) 295 return; 296 } 297 } 298 } 299 } 300 301 protected: 302 // Implementation agnostic information 303 HeaderType m_header; 304 const uint32_t *m_hash_indexes; 305 const uint32_t *m_hash_values; 306 const uint32_t *m_hash_offsets; 307 }; 308}; 309 310#endif // liblldb_MappedHash_h_ 311