Add command execution with redirection

Expose command execution with pipes to stdin, stdout and stderr.

This will allow to read the result of adb commands.

app/src/sys/unix/process.c

@@ -1,5 +1,6 @@
 #include "util/process.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
@@ -50,65 +51,151 @@ search_executable(const char *file) {
 }
 
 enum process_result
-process_execute(const char *const argv[], pid_t *pid) {
-    int fd[2];
+process_execute_redirect(const char *const argv[], pid_t *pid, int *pipe_stdin,
+                     int *pipe_stdout, int *pipe_stderr) {
+    int in[2];
+    int out[2];
+    int err[2];
+    int internal[2]; // communication between parent and children
 
-    if (pipe(fd) == -1) {
+    if (pipe(internal) == -1) {
         perror("pipe");
         return PROCESS_ERROR_GENERIC;
     }
-
-    enum process_result ret = PROCESS_SUCCESS;
+    if (pipe_stdin) {
+        if (pipe(in) == -1) {
+            perror("pipe");
+            close(internal[0]);
+            close(internal[1]);
+            return PROCESS_ERROR_GENERIC;
+        }
+    }
+    if (pipe_stdout) {
+        if (pipe(out) == -1) {
+            perror("pipe");
+            // clean up
+            if (pipe_stdin) {
+                close(in[0]);
+                close(in[1]);
+            }
+            close(internal[0]);
+            close(internal[1]);
+            return PROCESS_ERROR_GENERIC;
+        }
+    }
+    if (pipe_stderr) {
+        if (pipe(err) == -1) {
+            perror("pipe");
+            // clean up
+            if (pipe_stdout) {
+                close(out[0]);
+                close(out[1]);
+            }
+            if (pipe_stdin) {
+                close(in[0]);
+                close(in[1]);
+            }
+            close(internal[0]);
+            close(internal[1]);
+            return PROCESS_ERROR_GENERIC;
+        }
+    }
 
     *pid = fork();
     if (*pid == -1) {
         perror("fork");
-        ret = PROCESS_ERROR_GENERIC;
-        goto end;
+        // clean up
+        if (pipe_stderr) {
+            close(err[0]);
+            close(err[1]);
+        }
+        if (pipe_stdout) {
+            close(out[0]);
+            close(out[1]);
+        }
+        if (pipe_stdin) {
+            close(in[0]);
+            close(in[1]);
+        }
+        close(internal[0]);
+        close(internal[1]);
+        return PROCESS_ERROR_GENERIC;
     }
 
-    if (*pid > 0) {
-        // parent close write side
-        close(fd[1]);
-        fd[1] = -1;
-        // wait for EOF or receive errno from child
-        if (read(fd[0], &ret, sizeof(ret)) == -1) {
-            perror("read");
-            ret = PROCESS_ERROR_GENERIC;
-            goto end;
-        }
-    } else if (*pid == 0) {
-        // child close read side
-        close(fd[0]);
-        if (fcntl(fd[1], F_SETFD, FD_CLOEXEC) == 0) {
-            execvp(argv[0], (char *const *)argv);
-            if (errno == ENOENT) {
-                ret = PROCESS_ERROR_MISSING_BINARY;
-            } else {
-                ret = PROCESS_ERROR_GENERIC;
+    if (*pid == 0) {
+        if (pipe_stdin) {
+            if (in[0] != STDIN_FILENO) {
+                dup2(in[0], STDIN_FILENO);
+                close(in[0]);
             }
+            close(in[1]);
+        }
+        if (pipe_stdout) {
+            if (out[1] != STDOUT_FILENO) {
+                dup2(out[1], STDOUT_FILENO);
+                close(out[1]);
+            }
+            close(out[0]);
+        }
+        if (pipe_stderr) {
+            if (err[1] != STDERR_FILENO) {
+                dup2(err[1], STDERR_FILENO);
+                close(err[1]);
+            }
+            close(err[0]);
+        }
+        close(internal[0]);
+        enum process_result err;
+        if (fcntl(internal[1], F_SETFD, FD_CLOEXEC) == 0) {
+            execvp(argv[0], (char *const *) argv);
             perror("exec");
+            err = errno == ENOENT ? PROCESS_ERROR_MISSING_BINARY
+                                  : PROCESS_ERROR_GENERIC;
         } else {
             perror("fcntl");
-            ret = PROCESS_ERROR_GENERIC;
+            err = PROCESS_ERROR_GENERIC;
         }
-        // send ret to the parent
-        if (write(fd[1], &ret, sizeof(ret)) == -1) {
+        // send err to the parent
+        if (write(internal[1], &err, sizeof(err)) == -1) {
             perror("write");
         }
-        // close write side before exiting
-        close(fd[1]);
+        close(internal[1]);
         _exit(1);
     }
 
-end:
-    if (fd[0] != -1) {
-        close(fd[0]);
+    // parent
+    assert(*pid > 0);
+
+    close(internal[1]);
+
+    enum process_result res = PROCESS_SUCCESS;
+    // wait for EOF or receive err from child
+    if (read(internal[0], &res, sizeof(res)) == -1) {
+        perror("read");
+        res = PROCESS_ERROR_GENERIC;
     }
-    if (fd[1] != -1) {
-        close(fd[1]);
+
+    close(internal[0]);
+
+    if (pipe_stdin) {
+        close(in[0]);
+        *pipe_stdin = in[1];
     }
-    return ret;
+    if (pipe_stdout) {
+        *pipe_stdout = out[0];
+        close(out[1]);
+    }
+    if (pipe_stderr) {
+        *pipe_stderr = err[0];
+        close(err[1]);
+    }
+
+    return res;
+}
+
+enum process_result
+process_execute(const char *const argv[], pid_t *pid) {
+    return process_execute_redirect(argv, pid, NULL, NULL, NULL);
 }
 
 bool
@@ -175,3 +262,15 @@ is_regular_file(const char *path) {
     }
     return S_ISREG(path_stat.st_mode);
 }
+
+ssize_t
+read_pipe(int pipe, char *data, size_t len) {
+    return read(pipe, data, len);
+}
+
+void
+close_pipe(int pipe) {
+    if (close(pipe)) {
+        perror("close pipe");
+    }
+}