From f59d82eb8fda3ddcf790556c6c3615e40ae8b15b Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Mon, 3 Oct 2022 21:23:22 +0300
Subject: Add support for 'for' loop second (... | for x) and third (for x
 <...) forms in script

---
 libbuild2/script/run.hxx | 66 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 62 insertions(+), 4 deletions(-)

(limited to 'libbuild2/script/run.hxx')

diff --git a/libbuild2/script/run.hxx b/libbuild2/script/run.hxx
index 01b010c..5d46d21 100644
--- a/libbuild2/script/run.hxx
+++ b/libbuild2/script/run.hxx
@@ -38,22 +38,24 @@ namespace build2
     // Location is the start position of this command line in the script. It
     // can be used in diagnostics.
     //
-    // Optionally, save the command output into the referenced variable. In
-    // this case assume that the expression contains a single pipline.
+    // Optionally, execute the specified function at the end of the pipe,
+    // either after the last command or instead of it.
     //
     void
     run (environment&,
          const command_expr&,
          const iteration_index*, size_t index,
          const location&,
-         string* output = nullptr);
+         const function<command_function>& = nullptr,
+         bool last_cmd = true);
 
     bool
     run_cond (environment&,
               const command_expr&,
               const iteration_index*, size_t index,
               const location&,
-              string* output = nullptr);
+              const function<command_function>& = nullptr,
+              bool last_cmd = true);
 
     // Perform the registered special file cleanups in the direct order and
     // then the regular cleanups in the reverse order.
@@ -80,6 +82,62 @@ namespace build2
     //
     string
     diag_path (const dir_name_view&);
+
+    // Read out the stream content into a string, optionally splitting the
+    // input data at whitespaces or newlines in which case return one
+    // sub-string at a time (see the set builtin options for the splitting
+    // semantics). Throw io_error on the underlying OS error.
+    //
+    // If the execution deadline is specified, then turn the stream into the
+    // non-blocking mode. If the specified deadline is reached while reading
+    // the stream, then bail out for the successful deadline and fail
+    // otherwise. Note that in the former case the result will be incomplete,
+    // but we leave it to the caller to handle that.
+    //
+    // Note that on Windows we can only turn pipe file descriptors into the
+    // non-blocking mode. Thus, we have no choice but to read from descriptors
+    // of other types synchronously there. That implies that we can
+    // potentially block indefinitely reading a file and missing the deadline
+    // on Windows. Note though, that the user can normally rewrite the
+    // command, for example, `set foo <<<file` with `cat file | set foo` to
+    // avoid this problem.
+    //
+    class stream_reader
+    {
+    public:
+      stream_reader (auto_fd&&,
+                     bool pipe,
+                     bool whitespace, bool newline, bool exact,
+                     const optional<deadline>&,
+                     const command& deadline_cmd,
+                     const location&);
+
+      // Return nullopt if eos is reached.
+      //
+      optional<string>
+      next ();
+
+    private:
+      ifdstream is_;
+      bool whitespace_;
+      bool newline_;
+      bool exact_;
+      optional<deadline> deadline_;
+      const command& deadline_cmd_;
+      const location& location_;
+
+      bool empty_ = true; // Set to false after the first character is read.
+    };
+
+    // Read the stream content using the stream reader in the no-split exact
+    // mode.
+    //
+    string
+    stream_read (auto_fd&&,
+                 bool pipe,
+                 const optional<deadline>&,
+                 const command& deadline_cmd,
+                 const location&);
   }
 }
 
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