chore: import upstream snapshot with attribution

src/butil/popen.cpp

@@ -0,0 +1,206 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+// Date: 2017/11/04 17:37:43
+
+#include <gflags/gflags.h>
+#include "butil/build_config.h"
+#include "butil/logging.h"
+
+#if defined(OS_LINUX)
+// clone is a linux specific syscall
+#include <sched.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+extern "C" {
+int BAIDU_WEAK bthread_usleep(uint64_t microseconds);
+}
+#endif
+
+namespace butil {
+
+#if defined(OS_LINUX)
+
+const int CHILD_STACK_SIZE = 256 * 1024;
+
+struct ChildArgs {
+    const char* cmd;
+    int pipe_fd0;
+    int pipe_fd1;
+};
+
+int launch_child_process(void* args) {
+    ChildArgs* cargs = (ChildArgs*)args;
+    dup2(cargs->pipe_fd1, STDOUT_FILENO);
+    close(cargs->pipe_fd0);
+    close(cargs->pipe_fd1);
+    execl("/bin/sh", "sh", "-c", cargs->cmd, NULL);
+    _exit(1);
+}
+
+int read_command_output_through_clone(std::ostream& os, const char* cmd) {
+    int pipe_fd[2];
+    if (pipe(pipe_fd) != 0) {
+        PLOG(ERROR) << "Fail to pipe";
+        return -1;
+    }
+    int saved_errno = 0;
+    int wstatus = 0;
+    pid_t cpid;
+    int rc = 0;
+    ChildArgs args = { cmd, pipe_fd[0], pipe_fd[1] };
+    char buffer[1024];
+
+    char* child_stack = NULL;
+    char* child_stack_mem = (char*)malloc(CHILD_STACK_SIZE);
+    if (!child_stack_mem) {
+        LOG(ERROR) << "Fail to alloc stack for the child process";
+        rc = -1;
+        goto END;
+    }
+    child_stack = child_stack_mem + CHILD_STACK_SIZE;  
+                               // ^ Assume stack grows downward
+    cpid = clone(launch_child_process, child_stack,
+                 __WCLONE | CLONE_VM | SIGCHLD | CLONE_UNTRACED, &args);
+    if (cpid < 0) {
+        PLOG(ERROR) << "Fail to clone child process";
+        rc = -1;
+        goto END;
+    }
+    close(pipe_fd[1]);
+    pipe_fd[1] = -1;
+
+    for (;;) {
+        const ssize_t nr = read(pipe_fd[0], buffer, sizeof(buffer));
+        if (nr > 0) {
+            os.write(buffer, nr);
+            continue;
+        } else if (nr == 0) {
+            break;
+        } else if (errno != EINTR) {
+            LOG(ERROR) << "Encountered error while reading for the pipe";
+            break;
+        }
+    }
+
+    close(pipe_fd[0]);
+    pipe_fd[0] = -1;
+
+    for (;;) {
+        pid_t wpid = waitpid(cpid, &wstatus, WNOHANG | __WALL);
+        if (wpid > 0) {
+            break;
+        }
+        if (wpid == 0) {
+            if (bthread_usleep != NULL) {
+                bthread_usleep(1000);
+            } else {
+                usleep(1000);
+            }
+            continue;
+        }
+        rc = -1;
+        goto END;
+    }
+
+    if (WIFEXITED(wstatus)) {
+        rc = WEXITSTATUS(wstatus);
+        goto END;
+    }
+
+    if (WIFSIGNALED(wstatus)) {
+        os << "Child process(" << cpid << ") was killed by signal "
+           << WTERMSIG(wstatus);
+    }
+
+    rc = -1;
+    errno = ECHILD;
+
+END:
+    saved_errno = errno;
+    if (child_stack_mem) {
+        free(child_stack_mem);
+    }
+    if (pipe_fd[0] >= 0) {
+        close(pipe_fd[0]);
+    }
+    if (pipe_fd[1] >= 0) {
+        close(pipe_fd[1]);
+    }
+    errno = saved_errno;
+    return rc;
+}
+
+DEFINE_bool(run_command_through_clone, false,
+            "(Linux specific) Run command with clone syscall to "
+            "avoid the costly page table duplication");
+
+#endif // OS_LINUX
+
+#include <stdio.h>
+
+int read_command_output_through_popen(std::ostream& os, const char* cmd) {
+    FILE* pipe = popen(cmd, "r");
+    if (pipe == NULL) {
+        return -1;
+    }
+    char buffer[1024];
+    for (;;) {
+        size_t nr = fread(buffer, 1, sizeof(buffer), pipe);
+        if (nr != 0) {
+            os.write(buffer, nr);
+        }
+        if (nr != sizeof(buffer)) {
+            if (feof(pipe)) {
+                break;
+            } else if (ferror(pipe)) {
+                LOG(ERROR) << "Encountered error while reading for the pipe";
+                break;
+            }
+            // retry;
+        }
+    }
+
+    const int wstatus = pclose(pipe);
+
+    if (wstatus < 0) {
+        return wstatus;
+    }
+    if (WIFEXITED(wstatus)) {
+        return WEXITSTATUS(wstatus);
+    }
+    if (WIFSIGNALED(wstatus)) {
+        os << "Child process was killed by signal "
+           << WTERMSIG(wstatus);
+    }
+    errno = ECHILD;
+    return -1;
+}
+
+int read_command_output(std::ostream& os, const char* cmd) {
+#if !defined(OS_LINUX)
+    return read_command_output_through_popen(os, cmd);
+#else
+    return FLAGS_run_command_through_clone
+        ? read_command_output_through_clone(os, cmd)
+        : read_command_output_through_popen(os, cmd);
+#endif
+}
+
+}  // namespace butil