1 files changed, 35 insertions, 4 deletions

diff --git a/lldb/source/Host/common/FileSystem.cpp b/lldb/source/Host/common/FileSystem.cpp
index 509a187e40e..5a5dbc79fe1 100644
--- a/lldb/source/Host/common/FileSystem.cpp
+++ b/lldb/source/Host/common/FileSystem.cpp
@@ -11,6 +11,7 @@
 
 #include "llvm/Support/MD5.h"
 
+#include <algorithm>
 #include <fstream>
 #include <vector>
 
@@ -20,22 +21,33 @@ using namespace lldb_private;
 namespace {
 
 bool
-CalcMD5(const FileSpec &file_spec, llvm::MD5::MD5Result &md5_result)
+CalcMD5(const FileSpec &file_spec, uint64_t offset, uint64_t length, llvm::MD5::MD5Result &md5_result)
 {
     llvm::MD5 md5_hash;
     std::ifstream file(file_spec.GetPath(), std::ios::binary);
     if (!file.is_open())
         return false;
 
+    if (offset > 0)
+        file.seekg(offset, file.beg);
+
     std::vector<char> read_buf(4096);
+    uint64_t total_read_bytes = 0;
     while (!file.eof())
     {
-        file.read(&read_buf[0], read_buf.size());
+        const uint64_t to_read = (length > 0) ?
+            std::min(static_cast<uint64_t>(read_buf.size()), length - total_read_bytes) :
+            read_buf.size();
+        if (to_read == 0)
+            break;
+
+        file.read(&read_buf[0], to_read);
         const auto read_bytes = file.gcount();
         if (read_bytes == 0)
             break;
 
         md5_hash.update(llvm::StringRef(&read_buf[0], read_bytes));
+        total_read_bytes += read_bytes;
     }
 
     md5_hash.final(md5_result);
@@ -47,8 +59,18 @@ CalcMD5(const FileSpec &file_spec, llvm::MD5::MD5Result &md5_result)
 bool
 FileSystem::CalculateMD5(const FileSpec &file_spec, uint64_t &low, uint64_t &high)
 {
+    return CalculateMD5(file_spec, 0, 0, low, high);
+}
+
+bool
+FileSystem::CalculateMD5(const FileSpec &file_spec,
+                         uint64_t offset,
+                         uint64_t length,
+                         uint64_t &low,
+                         uint64_t &high)
+{
     llvm::MD5::MD5Result md5_result;
-    if (!CalcMD5(file_spec, md5_result))
+    if (!CalcMD5(file_spec, offset, length, md5_result))
         return false;
 
     const auto uint64_res = reinterpret_cast<const uint64_t*>(md5_result);
@@ -61,8 +83,17 @@ FileSystem::CalculateMD5(const FileSpec &file_spec, uint64_t &low, uint64_t &hig
 bool
 FileSystem::CalculateMD5AsString(const FileSpec &file_spec, std::string& digest_str)
 {
+    return CalculateMD5AsString(file_spec, 0, 0, digest_str);
+}
+
+bool
+FileSystem::CalculateMD5AsString(const FileSpec &file_spec,
+                                 uint64_t offset,
+                                 uint64_t length,
+                                 std::string& digest_str)
+{
     llvm::MD5::MD5Result md5_result;
-    if (!CalcMD5(file_spec, md5_result))
+    if (!CalcMD5(file_spec, offset, length, md5_result))
         return false;
 
     llvm::SmallString<32> result_str;