Berry Webclient: Change StreamBytes to StreamBeBytesWriter, and improve wc_getbytes (#18837)

This reduces allocation to a single allocaiton, but also theroetically allows the Bytes object to grow if content-length was unset.

(cherry picked from commit 936477f5977dd1a4f899498cc7cc0baf05b34a89)

tasmota/tasmota_xdrv_driver/xdrv_52_3_berry_webclient.ino

@@ -654,21 +654,59 @@ extern "C" {
   }
 }
 
-class StreamBytes: public Stream
+
+// a stream which writes to the Bytes object on the top of the stack
+class StreamBeBytesWriter: public Stream
 {
 public:
-  StreamBytes(uint8_t * buf_in, int len_in) : buf(buf_in), offset(0), len(len_in) {};
+  StreamBeBytesWriter(bvm *vm_in, int increment = 1024) : vm(vm_in), offset(0), incr(increment) {};
 
   size_t write(const uint8_t *buffer, size_t size) override {
-    // AddLog(LOG_LEVEL_INFO, "FLASH: addr=%p  hex=%*_H  size=%i", addr_start + offset, 32, buffer, size);
-    if (size > 0) {
-      if (offset + size > len){
-        AddLog(LOG_LEVEL_ERROR, "BERRYWC: bufer overrun");
-        return size;
+    // we need size, not len, so can;t just get len with be_tobytes
+    be_getmember(vm, -1, ".size");
+    int32_t signed_size = be_toint(vm, -1);
+    be_pop(vm, 1);  /* bytes() instance is at top */
+
+    // if it won't fit, make the bytes object bigger
+    if (offset + size > signed_size){
+      int newsize = offset + size + incr;
+      AddLog(LOG_LEVEL_INFO, "BE: realloc bytes in StreamBeBytesWriter newsize=%i", newsize);
+      be_getmember(vm, -1, "resize");
+      be_pushvalue(vm, -2);
+      be_pushint(vm, size);
+      be_call(vm, 2); /* call b.resize(size) */
+      be_pop(vm, 3);  /* bytes() instance is at top */      
+
+      // checkw e got it, because Berry just maxes out?
+      be_getmember(vm, -1, ".size");
+      signed_size = be_toint(vm, -1);
+      be_pop(vm, 1);  /* bytes() instance is at top */
+      if (offset + size > signed_size){
+        // what should we raise here???
+        be_raise(vm, "alloc_error", "did not get enough extra bytes");
       }
-      memcpy(buf+offset, buffer, size);
-      offset += size;
     }
+
+    // AddLog(LOG_LEVEL_INFO, "FLASH: addr=%p  hex=%*_H  size=%i", addr_start + offset, 32, buffer, size);
+    if (offset + size > signed_size){
+      AddLog(LOG_LEVEL_ERROR, "BERRYWC: buffer overrun");
+      return size;
+    }
+
+    char *bytebuf = (char*) be_tobytes(vm, -1, NULL); /* we get the address of the internam buffer of size 'size' */
+    if (!bytebuf){
+      AddLog(LOG_LEVEL_ERROR, "BERRYWC: buffer null??");
+      return size;
+    }
+
+    // stream in our chunk
+    memcpy(bytebuf + offset, buffer, size);
+    offset += size;
+
+    // set the len
+    be_pushint(vm, offset);
+    be_setmember(vm, -2, ".len");
+    be_pop(vm, 1);
     return size;
   }
   size_t write(uint8_t data) override {
@@ -682,9 +720,9 @@ public:
   void flush() override { }
 
 protected:
-  uint8_t *buf;          // start address
+  bvm *vm;                // the berry VM
   uint32_t offset;       // how many bytes have already been written
-  uint32_t len;          // allocated len
+  size_t incr;           // amount to add to size if it does not fit.
 };
 
 extern "C" {
@@ -693,14 +731,16 @@ extern "C" {
     HTTPClientLight * cl = wc_getclient(vm);
     int32_t sz = cl->getSize();
     // abort if we exceed 32KB size, things will not go well otherwise
-    if (sz >= 32767 || sz < 0) {
-      be_raise(vm, "value_error", "response size -1 or too big (>32KB)");
+    if (sz >= 32767) {
+      be_raise(vm, "value_error", "response size too big (>32KB)");
     }
-    uint8_t * buf = (uint8_t*) be_pushbuffer(vm, sz);
-    StreamBytes memory_writer(buf, sz);
+    // default to 1K starter if contetn-length not present
+    if (sz < 0) sz = 1024;
+    // create a bytes object at top of stack.
+    // the streamwriter knows how to get it. 
+    uint8_t * buf = (uint8_t*) be_pushbytes(vm, nullptr, sz);
+    StreamBeBytesWriter memory_writer(vm);
     int32_t written = cl->writeToStream(&memory_writer);
-
-    be_pushbytes(vm, buf, sz);
     cl->end();  // free allocated memory ~16KB
     be_return(vm);  /* return code */
   }