[remote] try to enforce protocol state

src/tailer/tailer.main.c

@@ -219,11 +219,24 @@ void set_client_path_state_error(struct client_path_state *cps, const char *op)
     delete_client_path_list(&cps->cps_children);
 }
 
-static int readall(int sock, void *buf, size_t len)
+typedef enum {
+    RS_ERROR,
+    RS_PACKET_TYPE,
+    RS_PAYLOAD_TYPE,
+    RS_PAYLOAD,
+    RS_PAYLOAD_LENGTH,
+    RS_PAYLOAD_CONTENT,
+} recv_state_t;
+
+static recv_state_t readall(recv_state_t state, int sock, void *buf, size_t len)
 {
     char *cbuf = (char *) buf;
     off_t offset = 0;
 
+    if (state == RS_ERROR) {
+        return RS_ERROR;
+    }
+
     while (len > 0) {
         ssize_t rc = read(sock, &cbuf[offset], len);
 
@@ -233,12 +246,12 @@ static int readall(int sock, void *buf, size_t len)
                 case EINTR:
                     break;
                 default:
-                    return -1;
+                    return RS_ERROR;
             }
         }
         else if (rc == 0) {
             errno = EIO;
-            return -1;
+            return RS_ERROR;
         }
         else {
             len -= rc;
@@ -246,20 +259,38 @@ static int readall(int sock, void *buf, size_t len)
         }
     }
 
-    return 0;
+    switch (state) {
+        case RS_PACKET_TYPE:
+            return RS_PAYLOAD_TYPE;
+        case RS_PAYLOAD_TYPE:
+            return RS_PAYLOAD;
+        case RS_PAYLOAD_LENGTH:
+            return RS_PAYLOAD_CONTENT;
+        case RS_PAYLOAD_CONTENT:
+            return RS_PAYLOAD_TYPE;
+        default:
+            return RS_ERROR;
+    }
 }
 
-static tailer_packet_payload_type_t read_payload_type(int sock)
+static tailer_packet_payload_type_t read_payload_type(recv_state_t *state, int sock)
 {
     tailer_packet_payload_type_t retval = TPPT_DONE;
 
-    readall(sock, &retval, sizeof(retval));
+    assert(*state == RS_PAYLOAD_TYPE);
+
+    *state = readall(*state, sock, &retval, sizeof(retval));
+    if (*state != RS_ERROR && retval == TPPT_DONE) {
+        *state = RS_PACKET_TYPE;
+    }
     return retval;
 }
 
-static char *readstr(int sock)
+static char *readstr(recv_state_t *state, int sock)
 {
-    tailer_packet_payload_type_t payload_type = read_payload_type(sock);
+    assert(*state == RS_PAYLOAD_TYPE);
+
+    tailer_packet_payload_type_t payload_type = read_payload_type(state, sock);
 
     if (payload_type != TPPT_STRING) {
         fprintf(stderr, "error: expected string, got: %d\n", payload_type);
@@ -268,7 +299,9 @@ static char *readstr(int sock)
 
     int32_t length;
 
-    if (readall(sock, &length, sizeof(length)) == -1) {
+    *state = RS_PAYLOAD_LENGTH;
+    *state = readall(*state, sock, &length, sizeof(length));
+    if (*state == RS_ERROR) {
         fprintf(stderr, "error: unable to read string length\n");
         return NULL;
     }
@@ -278,7 +311,8 @@ static char *readstr(int sock)
         return NULL;
     }
 
-    if (readall(sock, retval, length) == -1) {
+    *state = readall(*state, sock, retval, length);
+    if (*state == RS_ERROR) {
         fprintf(stderr, "error: unable to read string of length: %d\n", length);
         free(retval);
         return NULL;
@@ -288,16 +322,18 @@ static char *readstr(int sock)
     return retval;
 }
 
-static int readint64(int sock, int64_t *i)
+static int readint64(recv_state_t *state, int sock, int64_t *i)
 {
-    tailer_packet_payload_type_t payload_type = read_payload_type(sock);
+    tailer_packet_payload_type_t payload_type = read_payload_type(state, sock);
 
     if (payload_type != TPPT_INT64) {
         fprintf(stderr, "error: expected int64, got: %d\n", payload_type);
         return -1;
     }
 
-    if (readall(sock, i, sizeof(*i)) == -1) {
+    *state = RS_PAYLOAD_CONTENT;
+    *state = readall(*state, sock, i, sizeof(*i));
+    if (*state == -1) {
         fprintf(stderr, "error: unable to read int64\n");
         return -1;
     }
@@ -581,6 +617,7 @@ int poll_paths(struct list *path_list)
 int main(int argc, char *argv[])
 {
     int done = 0, timeout = 0;
+    recv_state_t rstate = RS_PACKET_TYPE;
 
     list_init(&client_path_list);
 
@@ -596,7 +633,9 @@ int main(int argc, char *argv[])
         if (ready_count) {
             tailer_packet_type_t type;
 
-            if (readall(STDIN_FILENO, &type, sizeof(type)) == -1) {
+            assert(rstate == RS_PACKET_TYPE);
+            rstate = readall(rstate, STDIN_FILENO, &type, sizeof(type));
+            if (rstate == RS_ERROR) {
                 fprintf(stderr, "info: exiting...\n");
                 done = 1;
             } else {
@@ -604,11 +643,11 @@ int main(int argc, char *argv[])
                     case TPT_OPEN_PATH:
                     case TPT_CLOSE_PATH:
                     case TPT_LOAD_PREVIEW: {
-                        const char *path = readstr(STDIN_FILENO);
+                        const char *path = readstr(&rstate, STDIN_FILENO);
                         int64_t preview_id = 0;
 
                         if (type == TPT_LOAD_PREVIEW) {
-                            if (readint64(STDIN_FILENO, &preview_id) == -1) {
+                            if (readint64(&rstate, STDIN_FILENO, &preview_id) == -1) {
                                 done = 1;
                                 break;
                             }
@@ -616,7 +655,7 @@ int main(int argc, char *argv[])
                         if (path == NULL) {
                             fprintf(stderr, "error: unable to get path to open\n");
                             done = 1;
-                        } else if (read_payload_type(STDIN_FILENO) != TPPT_DONE) {
+                        } else if (read_payload_type(&rstate, STDIN_FILENO) != TPPT_DONE) {
                             fprintf(stderr, "error: invalid open packet\n");
                             done = 1;
                         } else if (type == TPT_OPEN_PATH) {
@@ -773,13 +812,13 @@ int main(int argc, char *argv[])
                     }
                     case TPT_ACK_BLOCK:
                     case TPT_NEED_BLOCK: {
-                        char *path = readstr(STDIN_FILENO);
+                        char *path = readstr(&rstate, STDIN_FILENO);
 
                         // fprintf(stderr, "info: block packet path: %s\n", path);
                         if (path == NULL) {
                             fprintf(stderr, "error: unable to get block path\n");
                             done = 1;
-                        } else if (read_payload_type(STDIN_FILENO) != TPPT_DONE) {
+                        } else if (read_payload_type(&rstate, STDIN_FILENO) != TPPT_DONE) {
                             fprintf(stderr, "error: invalid block packet\n");
                             done = 1;
                         } else {