Embedded XML Parser
saxml is a truly small event-driven XML parser designed for use in embedded/microcontroller applications.
Since saxml is a SAX XML parser (see https://en.wikipedia.org/wiki/Simple_API_for_XML), the parser has a very small memory footprint (there's no XML document stored on the heap). Instead, the XML document is streamed to the parser a single character at a time. As the parser encounters interesting events (such as a start tag, end tag, attribute, etc.), the parser executes callback functions which are registered by the calling application. This allows the calling application to perform application-specific operations based on XML parsing events.
The parse depth and heirarchy can easily be maintained by an application through the use of a stack; push the tag name on the stack each time a tagHandler event is handled and pop the top element off the stack each time a tagEndHandler event is handled.
See the test subdirectory for a simple example application. include/saxml/saxml.h includes a detailed description of the API.
saxml performs no validation of the XML document
Add to the following line to your project's platformio.ini file: lib_deps = https://github.com/zorxx/saxml.
PlatformIO will automatically download the code and set the include path when building. The library can be used by adding #include "saxml/saxml.h" in the source files.
Example platformio.ini file:
[env]
platform = espressif32
framework = espidf
monitor_speed = 115200
[common]
lib_deps = https://github.com/zorxx/saxml
[env:nodemcu-32s]
board = nodemcu-32s
board_build.filesystem = littlefs
board_build.partitions = min_littlefs.csv
lib_deps = ${common.lib_deps}
XML Document:
<begin >
<second_begin>
<nothing_much/>
content
</second_begin>
</begin>Callbacks executed:
tagHandler: 'begin'
tagHandler: 'second_begin'
tagHandler: 'nothing_much'
tagEndHandler: 'nothing_much'
contentHandler: 'content
'
tagEndHandler: 'second_begin'
tagEndHandler: 'begin'
XML Document:
<begin >
<second_begin yes no="hello">
<nothing_much/>content</second_begin>
more content goes here
</begin>Callbacks executed:
tagHandler: 'begin'
tagHandler: 'second_begin'
attributeHandler: 'yes'
attributeHandler: 'no="hello"'
tagHandler: 'nothing_much'
tagEndHandler: 'nothing_much'
contentHandler: 'content'
tagEndHandler: 'second_begin'
contentHandler: 'more content goes here
'
tagEndHandler: 'begin'
XML Document:
<begin >
<second_begin yes no="hello">
<nothing_much attribute_in_small_tag />
<another_begin>
</another_begin>
</second_begin>
more content goes here
</begin>Callbacks executed:
tagHandler: 'begin'
tagHandler: 'second_begin'
attributeHandler: 'yes'
attributeHandler: 'no="hello"'
tagHandler: 'nothing_much'
attributeHandler: 'attribute_in_small_tag'
tagEndHandler: ' '
tagHandler: 'another_begin'
tagEndHandler: 'another_begin'
tagEndHandler: 'second_begin'
contentHandler: 'more content goes here
'
tagEndHandler: 'begin'
Note that, in this example, the tagEndHandler is called with a single-character string parameter for the empty tag (nothing_much) that contains an attribute. This is an ideosyncrasy of the SAX parser, since the empty tag's name isn't stored by the parser, in order to save heap usage.