smbios-parser

Small C99 and C++98 library to parse SMBIOS information.

The SMBIOS (System Management BIOS) is a standard specification that specifies how system vendors present management information about their products. It extends the BIOS interface on Intel architecture systems and allow operating systems (or programs) to retrieve information about the hardware without needing to probe it directly.

This library is a small and standalone implementation of the specification for C and C++ applications. You can also use the shared library with any C-compatible programming language (i.e. Python, Go, Java).

Usage

The library can be used in C and C++ applications in the following ways:

• As a static or shared library;
• Copying the files smbios.h and smbios.c into your project.

Once selected the preferred integration method, the library can be used as follows:

#include <smbios.h> int main(int argc, char *argv[]) { (void) argc; (void) argv; // Get SMBIOS information using a custom function. // An example in C for Windows and Linux can be found // in 'smbios_decode.c'. const uint8_t *data = NULL; size_t size = 0; load_smbios_data(&data, &size); // initialize the parser (the desired SMBIOS version is 3.0) struct ParserContext context; if (smbios_initialize(&context, data, size, SMBIOS_3_0) != SMBERR_OK) return 1; // iterate over the SMBIOS entries const struct Entry *entry = NULL; while (smbios_next(&context, &entry) == SMBERR_OK) { // do something with the current entry } return 0; }

The pointer to the current SMBIOS entry is stored in the variable specified as the second parameter of the smbios_next function. The entry is defined by the structure Entry and some of its most important fields are:

• type - Entry type, as defined in the SMBIOS specification;
• handle - Entry handle, a unique 16-bit number in the range 0 to 0FFFEh (for version 2.0) or 0 to 0FEFFh (for version 2.1 and later);
• data - Union with the actual formatted data of the entry for each supported type. Supported types are listed in the EntryType enumeration. The structured data for a type TYPE_XYZ is stored in a field named xyz in the data union (e.g. TYPE_BIOS_INFO data is stored in the field data.bios_info). If the entry type is not supported, you can still read its data from rawdata field.
• rawdata - Raw SMBIOS data of the entry (header and data itself).
• length - Length of the SMBIOS data in rawdata field.
• strings - Pointer to the start of the string table;
• string_count - Number of strings in the string table.

The library do not make heap allocations: everything is done in-place using the provided SMBIOS buffer and the context.

API

The following functions are available. If you’re using the library in a C++ code, the functions will be defined in the smbios namespace.

smbios_initialize

int smbios_initialize(struct ParserContext *context, const uint8_t *data, size_t size, int version )

Initialize the SMBIOS parser.

If the actual version of the SMBIOS data is smaller than the value of the parameter version, the parser will use the version of the SMBIOS data. Fields related to SMBIOS versions not selected will be left blank. Valid values are the ones defined in the enumeration SpecVersion.

• context: Parser context.
• data: SMBIOS data.
• size: Size of the SMBIOS data.
• version: Preferred SMBIOS version.

The function returns SMBERR_OK on success or a negative error code.

smbios_next

int smbios_next(struct ParserContext *context, const struct Entry **entry)

Get the next SMBIOS entry.

Calling this function invalidates any previously returned entry.

• context: Parser context.
• entry: Pointer to the entry.

The function returns SMBERR_OK on success or a negative error code.

smbios_reset

int smbios_reset(struct ParserContext *context)

Reset the SMBIOS parser and let it start from the beginning.

If the parser failed (e.g. invalid SMBIOS data), calling this function will fail too.

• context: Parser context.

The function returns SMBERR_OK on success or a negative error code.

smbios_get_version

int smbios_get_version(struct ParserContext *context, int *selected, int *original)

Returns the selected and/or the original SMBIOS versions.

• context: Parser context.
• selected: (optional) Selected version used to parse the SMBIOS data.
• original: (optional) Version of the SMBIOS data.

The function returns SMBERR_OK on success or a negative error code.

smbios_get_string

const char *smbios_get_string( const struct Entry *entry, int index )

Returns a string from the SMBIOS entry.

Fields in the entry that reference a string are automatically set with the corresponding string pointer. However, some entry types have an arbitrary number of strings not pointed by entry fields (e.g. the OEMStrings entry type). In this case, you can use this function to retrieve them.

This is a utility function to retrieve a string from the SMBIOS entry. The function will iterate over the strings in the SMBIOS entry and return the string with the given index, starting from 1. If the index is out of range, the function will return NULL.

If you want to avoid the overhead of the iteration for each call, you can access the string table directly. The start of the string table is set in the field strings of the entry. Each string is terminated with a null (00h) byte and the table is terminated with an additional null (00h) byte. The amount of strings is given in the field string_count of the entry.

• entry: SMBIOS entry.
• index: Index of the string, starting from 1.

The function returns the string associated with the given index or NULL in case of error.

License

The library is distributed under Apache License 2.0.