1 files changed, 265 insertions, 0 deletions
diff --git a/flang/lib/Parser/source.cpp b/flang/lib/Parser/source.cpp
new file mode 100644
index 0000000..0fbb8e3
--- /dev/null
+++ b/flang/lib/Parser/source.cpp
@@ -0,0 +1,265 @@
+//===-- lib/Parser/source.cpp ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Parser/source.h"
+#include "flang/Common/idioms.h"
+#include "flang/Parser/char-buffer.h"
+#include <algorithm>
+#include <cerrno>
+#include <cstddef>
+#include <cstring>
+#include <fcntl.h>
+#include <memory>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <vector>
+
+// TODO: Port to Windows &c.
+
+namespace Fortran::parser {
+
+static constexpr bool useMMap{true};
+static constexpr int minMapFileBytes{1};  // i.e., no minimum requirement
+static constexpr int maxMapOpenFileDescriptors{100};
+static int openFileDescriptors{0};
+
+SourceFile::~SourceFile() { Close(); }
+
+static std::vector<std::size_t> FindLineStarts(
+    const char *source, std::size_t bytes) {
+  std::vector<std::size_t> result;
+  if (bytes > 0) {
+    CHECK(source[bytes - 1] == '\n' && "missing ultimate newline");
+    std::size_t at{0};
+    do {
+      result.push_back(at);
+      const void *vp{static_cast<const void *>(&source[at])};
+      const void *vnl{std::memchr(vp, '\n', bytes - at)};
+      const char *nl{static_cast<const char *>(vnl)};
+      at = nl + 1 - source;
+    } while (at < bytes);
+    result.shrink_to_fit();
+  }
+  return result;
+}
+
+void SourceFile::RecordLineStarts() {
+  lineStart_ = FindLineStarts(content_, bytes_);
+}
+
+// Check for a Unicode byte order mark (BOM).
+// Module files all have one; so can source files.
+void SourceFile::IdentifyPayload() {
+  content_ = address_;
+  bytes_ = size_;
+  if (content_) {
+    static constexpr int BOMBytes{3};
+    static const char UTF8_BOM[]{"\xef\xbb\xbf"};
+    if (bytes_ >= BOMBytes && std::memcmp(content_, UTF8_BOM, BOMBytes) == 0) {
+      content_ += BOMBytes;
+      bytes_ -= BOMBytes;
+      encoding_ = Encoding::UTF_8;
+    }
+  }
+}
+
+std::string DirectoryName(std::string path) {
+  auto lastSlash{path.rfind("/")};
+  return lastSlash == std::string::npos ? path : path.substr(0, lastSlash);
+}
+
+std::string LocateSourceFile(
+    std::string name, const std::vector<std::string> &searchPath) {
+  if (name.empty() || name == "-" || name[0] == '/') {
+    return name;
+  }
+  for (const std::string &dir : searchPath) {
+    std::string path{dir + '/' + name};
+    struct stat statbuf;
+    if (stat(path.c_str(), &statbuf) == 0 && !S_ISDIR(statbuf.st_mode)) {
+      return path;
+    }
+  }
+  return name;
+}
+
+static std::size_t RemoveCarriageReturns(char *buffer, std::size_t bytes) {
+  std::size_t wrote{0};
+  char *p{buffer};
+  while (bytes > 0) {
+    void *vp{static_cast<void *>(p)};
+    void *crvp{std::memchr(vp, '\r', bytes)};
+    char *crcp{static_cast<char *>(crvp)};
+    if (!crcp) {
+      std::memmove(buffer + wrote, p, bytes);
+      wrote += bytes;
+      break;
+    }
+    std::size_t chunk = crcp - p;
+    std::memmove(buffer + wrote, p, chunk);
+    wrote += chunk;
+    p += chunk + 1;
+    bytes -= chunk + 1;
+  }
+  return wrote;
+}
+
+bool SourceFile::Open(std::string path, std::stringstream *error) {
+  Close();
+  path_ = path;
+  std::string errorPath{"'"s + path + "'"};
+  errno = 0;
+  fileDescriptor_ = open(path.c_str(), O_RDONLY);
+  if (fileDescriptor_ < 0) {
+    *error << "Could not open " << errorPath << ": " << std::strerror(errno);
+    return false;
+  }
+  ++openFileDescriptors;
+  return ReadFile(errorPath, error);
+}
+
+bool SourceFile::ReadStandardInput(std::stringstream *error) {
+  Close();
+  path_ = "standard input";
+  fileDescriptor_ = 0;
+  return ReadFile(path_, error);
+}
+
+bool SourceFile::ReadFile(std::string errorPath, std::stringstream *error) {
+  struct stat statbuf;
+  if (fstat(fileDescriptor_, &statbuf) != 0) {
+    *error << "fstat failed on " << errorPath << ": " << std::strerror(errno);
+    Close();
+    return false;
+  }
+  if (S_ISDIR(statbuf.st_mode)) {
+    *error << errorPath << " is a directory";
+    Close();
+    return false;
+  }
+
+  // Try to map a large source file into the process' address space.
+  // Don't bother with small ones.  This also helps keep the number
+  // of open file descriptors from getting out of hand.
+  if (useMMap && S_ISREG(statbuf.st_mode)) {
+    size_ = static_cast<std::size_t>(statbuf.st_size);
+    if (size_ >= minMapFileBytes &&
+        openFileDescriptors <= maxMapOpenFileDescriptors) {
+      void *vp = mmap(0, size_, PROT_READ, MAP_SHARED, fileDescriptor_, 0);
+      if (vp != MAP_FAILED) {
+        address_ = static_cast<const char *>(const_cast<const void *>(vp));
+        IdentifyPayload();
+        if (bytes_ > 0 && content_[bytes_ - 1] == '\n' &&
+            std::memchr(static_cast<const void *>(content_), '\r', bytes_) ==
+                nullptr) {
+          isMemoryMapped_ = true;
+          RecordLineStarts();
+          return true;
+        }
+        // The file needs to have its line endings normalized to simple
+        // newlines.  Remap it for a private rewrite in place.
+        vp = mmap(
+            vp, size_, PROT_READ | PROT_WRITE, MAP_PRIVATE, fileDescriptor_, 0);
+        if (vp != MAP_FAILED) {
+          address_ = static_cast<const char *>(const_cast<const void *>(vp));
+          IdentifyPayload();
+          auto mutableContent{const_cast<char *>(content_)};
+          bytes_ = RemoveCarriageReturns(mutableContent, bytes_);
+          if (bytes_ > 0) {
+            if (mutableContent[bytes_ - 1] == '\n' ||
+                (bytes_ & 0xfff) != 0 /* don't cross into next page */) {
+              if (mutableContent[bytes_ - 1] != '\n') {
+                // Append a final newline.
+                mutableContent[bytes_++] = '\n';
+              }
+              bool isNowReadOnly{mprotect(vp, bytes_, PROT_READ) == 0};
+              CHECK(isNowReadOnly);
+              content_ = mutableContent;
+              isMemoryMapped_ = true;
+              RecordLineStarts();
+              return true;
+            }
+          }
+        }
+        munmap(vp, size_);
+        address_ = content_ = nullptr;
+        size_ = bytes_ = 0;
+      }
+    }
+  }
+
+  // Read it into an expandable buffer, then marshal its content into a single
+  // contiguous block.
+  CharBuffer buffer;
+  while (true) {
+    std::size_t count;
+    char *to{buffer.FreeSpace(&count)};
+    ssize_t got{read(fileDescriptor_, to, count)};
+    if (got < 0) {
+      *error << "could not read " << errorPath << ": " << std::strerror(errno);
+      Close();
+      return false;
+    }
+    if (got == 0) {
+      break;
+    }
+    buffer.Claim(got);
+  }
+  if (fileDescriptor_ > 0) {
+    close(fileDescriptor_);
+    --openFileDescriptors;
+  }
+  fileDescriptor_ = -1;
+  normalized_ = buffer.MarshalNormalized();
+  address_ = normalized_.c_str();
+  size_ = normalized_.size();
+  IdentifyPayload();
+  RecordLineStarts();
+  return true;
+}
+
+void SourceFile::Close() {
+  if (useMMap && isMemoryMapped_) {
+    munmap(reinterpret_cast<void *>(const_cast<char *>(address_)), size_);
+    isMemoryMapped_ = false;
+  } else if (!normalized_.empty()) {
+    normalized_.clear();
+  } else if (address_) {
+    delete[] address_;
+  }
+  address_ = content_ = nullptr;
+  size_ = bytes_ = 0;
+  if (fileDescriptor_ > 0) {
+    close(fileDescriptor_);
+    --openFileDescriptors;
+  }
+  fileDescriptor_ = -1;
+  path_.clear();
+}
+
+SourcePosition SourceFile::FindOffsetLineAndColumn(std::size_t at) const {
+  CHECK(at < bytes_);
+  if (lineStart_.empty()) {
+    return {*this, 1, static_cast<int>(at + 1)};
+  }
+  std::size_t low{0}, count{lineStart_.size()};
+  while (count > 1) {
+    std::size_t mid{low + (count >> 1)};
+    if (lineStart_[mid] > at) {
+      count = mid - low;
+    } else {
+      count -= mid - low;
+      low = mid;
+    }
+  }
+  return {*this, static_cast<int>(low + 1),
+      static_cast<int>(at - lineStart_[low] + 1)};
+}
+}