How to obtain length of binary COMPONENT_EMBED_FILES

[papaluna]

What is the simplest way to obtain the length in bytes of an embedded binary file when using https://docs.espressif.com/projects/esp ... inary-data?

Is an attribute available which returns the length or do I have to compute it myself?

This is the way I do it right now:

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COMPONENT_EMBED_FILES := kafka_status_ok.message

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extern const uint8_t kafka_status_ok_message_start[] asm("_binary_kafka_status_ok_message_start");
extern const uint8_t kafka_status_ok_message_end[] asm("_binary_kafka_status_ok_message_end");

int len_buffer = sizeof(uint8_t) * (kafka_status_ok_message_end - kafka_status_ok_message_start);

[ESP_igrr]

The way you are doing this now seems to be the correct one. I don't think there is any better option when using just COMPONENT_EMBED_FILES without any extra logic.

(extra logic would be: determine size of the file at Make run time, store it as a variable, add -DMY_FILE_LEN=$(length_var) to CPPFLAGS...)

[papaluna]

Thanks.

[FiwiDev]

The way you are doing this now seems to be the correct one. I don't think there is any better option when using just COMPONENT_EMBED_FILES without any extra logic.

(extra logic would be: determine size of the file at Make run time, store it as a variable, add -DMY_FILE_LEN=$(length_var) to CPPFLAGS...)

I was digging through a compiled MAP output (trying to find the actual handles the compiler used for the embedded files), and noticed that there appears to be a "size" attribute also provided. See below...

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_binary_web_index_htm_end                         .pio/build/esp32dev/index.htm.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o
_binary_web_index_htm_size                        .pio/build/esp32dev/index.htm.txt.o
_binary_web_index_htm_start                       .pio/build/esp32dev/index.htm.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o
_binary_web_script_js_end                         .pio/build/esp32dev/script.js.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o
_binary_web_script_js_size                        .pio/build/esp32dev/script.js.txt.o
_binary_web_script_js_start                       .pio/build/esp32dev/script.js.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o
_binary_web_style_css_end                         .pio/build/esp32dev/style.css.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o
_binary_web_style_css_size                        .pio/build/esp32dev/style.css.txt.o
_binary_web_style_css_start                       .pio/build/esp32dev/style.css.txt.o
                                                  .pio/build/esp32dev/src/wifi.cpp.o

I'm not well versed in the binutils, i.e. trying to figure out if that symbol is actually mapped to a memory address, what size the symbol is (assuming 32-bit?), and what value it is. Tried defining an "asm("")" to reference the corresponding "*_size" entry to a size_t, but it just crashes the ESP32 every time I try to access it.

I mean, doing "end - start" is one way to get the length--but heck, if there's a better way...what's the trick?