Remove floats from block calculations, fix regression in 0e67846 espr…

…essif#53

Float argument strayed into flash_begin() size, caused erase sizes to be
calculated as too long. This triggered an error when writing near the end of
the flash, it would ask for erasing beyond the end of available space.

Closes espressif#60

esptool.py

@@ -415,6 +415,13 @@ def load_section(self, section):
 def arg_auto_int(x):
     return int(x, 0)
 
+def div_roundup(a, b):
+    """ Return a/b rounded up to nearest integer,
+    equivalent result to int(math.ceil(float(int(a)) / float(int(b))), only
+    without possible floating point accuracy errors.
+    """
+    return (int(a) + int(b) - 1) / int(b)
+
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description = 'ESP8266 ROM Bootloader Utility', prog = 'esptool')
 
@@ -532,7 +539,7 @@ def arg_auto_int(x):
         for (offset, size, data) in image.segments:
             print 'Downloading %d bytes at %08x...' % (size, offset),
             sys.stdout.flush()
-            esp.mem_begin(size, math.ceil(size / float(esp.ESP_RAM_BLOCK)), esp.ESP_RAM_BLOCK, offset)
+            esp.mem_begin(size, div_roundup(size, esp.ESP_RAM_BLOCK), esp.ESP_RAM_BLOCK, offset)
 
             seq = 0
             while len(data) > 0:
@@ -575,7 +582,7 @@ def arg_auto_int(x):
             args.addr_filename = args.addr_filename[2:]
             image = file(filename, 'rb').read()
             print 'Erasing flash...'
-            blocks = math.ceil(len(image)/float(esp.ESP_FLASH_BLOCK))
+            blocks = div_roundup(len(image), esp.ESP_FLASH_BLOCK)
             esp.flash_begin(blocks*esp.ESP_FLASH_BLOCK, address)
             seq = 0
             while len(image) > 0:
@@ -658,7 +665,7 @@ def arg_auto_int(x):
 
     elif args.operation == 'read_flash':
         print 'Please wait...'
-        file(args.filename, 'wb').write(esp.flash_read(args.address, 1024, int(math.ceil(args.size / 1024.)))[:args.size])
+        file(args.filename, 'wb').write(esp.flash_read(args.address, 1024, div_roundup(args.size, 1024))[:args.size])
 
     elif args.operation == 'erase_flash':
         esp.flash_erase()