Host Library

This Components provides the core functionality for the Host Emulator:

Sockets

Classes to provide simple Berkeley socket support for both Linux and Windows

Options

Command line argument parsing. Applications may pass parameters and access them using the CommandLine.

Startup

Initialises SPI Flash Emulation, Uart server (in Host Drivers) and LWIP networking, then enters the main task loop. This loop services LWIP plus the task and timer queues (implemented in Host ESP HAL). The Ctrl+C keypress is trapped to provide an orderly exit. If the system has become stuck in a loop or is otherwise unresponsive, subsequent Ctrl+C presses will force a process termination.

Threads and Interrupts

The emulator uses Posix threads (pthread library) to perform background processing which would probably be done in hardware or which is outside of the framework.

Ideally we’d use SCHED_FIFO to disable time-slicing and more closely resemble how interrupts work on a single-core CPU. However, this mode isn’t supported in Windows, and Linux requires privileged access and can potentially crash the system. Best avoided, I think.

All ESP code runs at a specific interrupt level, where 0 represents regular code. Interrupts are triggered from a separate thread (a CThread instance) which calls :cpp:func:` When an interrupt occurs, the level is raised according to the priority of that interrupt. Until that code has finished, only interrupts of a higher priority will preempt it.

Thread ‘interrupt’ code is sandwiched between calls to interrupt_begin() and interrupt_end(), which blocks interrupts from other threads at the same or lower level. The threads aren’t suspended but will block if they call interrupt_begin(). However, the main thread (level 0) is halted to reflect normal interrupt behaviour.

HOST_PARAMETERS

Set this value to pass additional parameters to a Host application. For example:

make run HOST_PARAMETERS='param1=12 param2="parameter with spaces"'
make run HOST_PARAMETERS="param1=12 param2=\"parameter with spaces\""

See Basic Utility for a worked example.

API

class CommandLine

Provides access to the command line.

Anything which doesn’t start with - is interpreted as an application parameter. For example: 

    app param1=value
Parameters which start with - are handled by the Host Emulator. Anything after -- is passed directly to the application: 
    app -- --debug --verbose

Public Functions

inline const Parameters &getParameters()

Fetch a reference to the list of command-line parameters.

struct Parameter

Manages a single parameter, may be optionally separated into name=value.

Public Functions

String getName() const

Get parameter name, if there is one.

String getValue() const

Get parameter value.

Public Members

const char *text = {nullptr}

The text exactly as presented on the command line.

class Parameters : public Vector<Parameter>

List of command-line parameters, in order.

Public Functions

Parameter find(const String &name) const

Fetch parameter by name.

Parameters:

name – Search is case-sensitive

Parameter findIgnoreCase(const String &name) const

Fetch parameter by name.

Parameters:

name – Search is NOT case-sensitive

References

Used by

Environment Variables

SoC support

  • host