main: redesign boot_out.txt writing #5536
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New design: * capture output to a vstr * compare the complete vstr to boot_out.txt * rewrite if not a complete match This is resilient against future changes to the automatic text written to boot_out.txt. This also fixes rewriting boot_out.txt in the case where boot.py prints something. Perhaps it also saves a bit of code space. Some tricks: * no need to close a file in read mode * no need to switch on/off USB write access, going down to the oofatfs layer doesn't check it anyway
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What happens if a write goes past the end of the vstr? Does it just discard the overflow?
How did you test? The easiest way I found to test whether a rewrite happened or not was to lengthen the 1 second delay to 10 seconds. I had a code.py that blinked board.LED, so I knew when it started.
The allocation is increased, until it fails. This means you could now MemoryError yourself if
I temporarily had code that turned the LED red during the 1 second delay before writing out the file. After changing boot.py to output something else and hitting reset, I would get the red LED once but not the next time I hit reset. |
That's a bit of a pathological case, but I think the exception should be caught if possible so you don't get no output, which is what would happen. |
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If it's hard to catch the MemoryError, then you could just truncate the output after some relatively small amount (a few thousand chars), and add an ellipsis or something. |
Now this boot.py:
```py
for i in range(1000):
print(i)
```
creates a 512-byte boot_out.txt that ends
```
88
89
...
```
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Now this boot.py: for i in range(1000):
print(i)creates a 512-byte boot_out.txt that ends |
Back in adafruit#5536 I modified how boot_out.txt got written. However, I broke USB enumeration in the safe-mode case. This fixes it so that a safe-mode board still connects on USB with all defaults. (tested on a macropad)
New design:
This is resilient against future changes to the automatic text written to boot_out.txt.
This also fixes rewriting boot_out.txt in the case where boot.py prints something.
Perhaps it also saves a bit of code space. Some tricks:
This is a possible alternative to