From d0c7f4712312f24a4b2e3919919dae1ebe7874c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=BA=90=E6=96=87=E9=9B=A8?=
 <41315874+fumiama@users.noreply.github.com>
Date: Fri, 6 May 2022 11:15:13 +0800
Subject: [PATCH] add more api

---
 protobuf.c        | 41 ++++++++++++++++++++++++++++++++++++++---
 simple_protobuf.h |  6 ++++++
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/protobuf.c b/protobuf.c
index d0cb37e..d6f70b1 100644
--- a/protobuf.c
+++ b/protobuf.c
@@ -5,9 +5,8 @@
 #include "simple_protobuf.h"
 
 static uint32_t read_num(FILE* fp) {
-    uint8_t c;
-    uint32_t n = 0;
-    uint8_t i = 0;
+    uint32_t c, n = 0;
+    long i = 0;
     do {
         c = fgetc(fp);
         if(feof(fp)) return n;
@@ -16,6 +15,18 @@ static uint32_t read_num(FILE* fp) {
     return n;
 }
 
+static uint32_t peek_num(FILE* fp) {
+    uint32_t c, n = 0;
+    long i = 0;
+    do {
+        c = fgetc(fp);
+        if(feof(fp)) return n;
+        else n |= (c & 0x7f) << (7 * i++);
+    } while((c & 0x80));
+    fseek(fp, -i, SEEK_CUR);
+    return n;
+}
+
 static int write_num(FILE* fp, uint32_t n) {
     char* c = (char*)(&n);
     int i = 0;
@@ -51,6 +62,30 @@ SIMPLE_PB* get_pb(FILE* fp) {
     return spb;
 }
 
+uint32_t get_pb_len(FILE* fp) {
+    uint32_t init_pos = ftell(fp);
+    uint32_t struct_len = peek_num(fp);
+    if(struct_len <= 1 || struct_len >= 1u<<20) return 0; // 1B<struct_len<1MB
+    return struct_len + 2*sizeof(uint32_t);
+}
+
+SIMPLE_PB* read_pb_into(FILE* fp, SIMPLE_PB* spb) {
+    if(!spb) return NULL;
+    uint32_t init_pos = ftell(fp);
+    uint32_t struct_len = read_num(fp);
+    if(struct_len <= 1 || struct_len >= 1u<<20) return NULL; // 1B<struct_len<1MB
+    spb->struct_len = struct_len;
+    memset(spb->target, 0, struct_len);
+    uint32_t offset, data_len;
+    for(char* p = spb->target; p < spb->target+struct_len; p += offset) {
+        offset = read_num(fp);
+        data_len = read_num(fp);
+        if(data_len > 0 && data_len <= offset) fread(p, data_len, 1, fp);
+    }
+    spb->real_len = ftell(fp) - init_pos;
+    return spb;
+}
+
 int set_pb(FILE* fp, uint32_t* items_len, uint32_t struct_len, void* target) {
     uint32_t offset = 0;
     uint32_t i = 0;
diff --git a/simple_protobuf.h b/simple_protobuf.h
index 4c0adc1..b3151b3 100644
--- a/simple_protobuf.h
+++ b/simple_protobuf.h
@@ -11,7 +11,13 @@ struct SIMPLE_PB {
 typedef struct SIMPLE_PB SIMPLE_PB;
 
 SIMPLE_PB* get_pb(FILE* fp);
+
+uint32_t get_pb_len(FILE* fp);
+
+SIMPLE_PB* read_pb_into(FILE* fp, SIMPLE_PB* spb);
+
 int set_pb(FILE* fp, uint32_t* items_len, uint32_t struct_len, void* target);
+
 //uint32_t struct_size, uint32_t items_cnt, void* item_addr1, void* item_addr2...
 uint32_t* align_struct(uint32_t struct_size, uint32_t items_cnt, ...);